Watch glossary

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Analogue Time Display

The time is indicated by a pair of hands. The current time is shown by the relative positions of the hour hand and minute hand. With a very few exceptions, nearly all high-quality wristwatches are equipped with analogue time displays. The electronic digital watches that dominated the market in the 1970s have since lost most of their importance.

Automatic Winding

An additional mechanism that uses the movements of the wearer’s arm as a source of energy to wind the mainspring of a mechanical watch. Abraham Louis Perrelet is credited with the invention of the portable watch with automatic winding. A self-taught watchmaker, Perrelet presented two different automatic winding constructions in 1770: one relied on an oscillating weight; the other on an unlimited turning rotor. Both were designed to make the winding key unnecessary. Automatic winding mechanisms on pocket watches couldn’t work efficiently because these watches don’t undergo sufficient motion, so the popularity of such mechanisms remained limited. Wristwatches, which are worn on one of the most active parts of the body, helped automatic winding to achieve a breakthrough. The beginning of this breakthrough is credited to Parisian watchmaker Léon Leroy in 1922. The first serially manufactured wristwatches with automatic winding were designed by Englishman John Harwood, who patented a corresponding mechanism in 1924. Rolex debuted the first wristwatch with (unidirectional) rotor winding in 1931. Felsa, the ébauche maker, introduced a bidirectionally winding rotor in 1942. Eterna’s ball-borne rotor, which debuted in 1948, blazed a trail for the self-winding systems that followed in ensuing years. After the “quartz crisis” had subsided somewhat, the renaissance of automatically winding wristwatches began in 1983.

Annual Calendar

Wristwatch which shows the correct date for the year-long interval from March 1 of one year to February 28 of the next year.

Adjust

The process of setting or regulating a timepiece.

Automatic Striking

The striking work of a pocket watch or wristwatch is automatic if, unlike the striking work of a repeater watch, it functions entirely without the need for manual intervention. Like a domestic clock, a watch with automatic striking audibly announces the arrival of the hours (petite sonnerie) or both the hours and the quarter hours (grande sonnerie). In response to the push of a button, these elaborate mechanisms can also be triggered to ring out the hours, quarter hours, and minutes.

Alarm

One of the first additional functions given to mechanical gear train timepieces, the first alarm mechanisms were crafted as early as the 16th century. They emit an audible signal when a preset moment arrives. Eterna patented one of the first alarm wristwatches in 1908. Well-known alarm wristwatches include Vulcain’s “Cricket” (which debuted in 1947), Jaeger-LeCoultre’s “Memovox” (which was introduced in 1951), and Omega’s “Memomatic” (which was launched in 1969). The alarm time on the “Memomatic” can be set with to-the-minute accuracy. Alarm

Baguette Caliber

An elongated rectangular caliber which was very popular in the 1920s and early 1930s. The ratio of its proportions (length to breadth) must be at least 3:1.

Beryllium

A silvery white, malleable metal extracted from beryl. Alloys containing beryllium are characterized by their extraordinary hardness, strength, and elasticity. Beryllium bronze is used in watches, e.g. to make balances. See also glucydur.

Bicolor Case

Watch case crafted from a combination of two differently colored metals, e.g. stainless steel and yellow gold, white gold and yellow gold, or red gold and yellow gold. The yellow parts of some bicolor cases are merely gold-plated.

Bimetallic Balance

Prior to the invention of the compensating balance spring, high-quality mechanical watches were usually equipped with bimetallic compensating balances. The rim, which is cut near the arms, consists of two metals (steel and brass) which have different coefficients of expansion when exposed to temperature changes. Changes in the moment of inertia of the balance compensate for the thermally induced changes in the length of a balance spring made of hardened steel.

Blue Hands and Screws

It has long been a tradition among horological craftsmen to blue the surfaces of steel components. Bluing requires a great deal of sensitivity and experience. The parts to be blued are placed in a small pan, which is then heated over a flame. The surfaces of these parts acquire the desired color when their temperature climbs to slightly less than 300 degrees Celsius.

Blind Person’s Wristwatch

A wristwatch with an especially robust dial train and a hinged crystal and bezel so that the sightless wearer can open the crystal, expose the dial, and “read” the position of the watch’s hands with his or her fingertips. The hour indices on watches for blind people are usually written in raised Braille numerals.

Breguet Overcoil Balance Spring

The decisive contribution towards the optimization of the balance spring was made by Abraham-Louis Breguet. This gifted watchmaker recognized the importance of the terminal curve for the concentric “breathing” of the balance spring. He debuted a type of spring which would later be known as the “Breguet overcoil” in 1795. The distinguishing characteristic of this type of spring is its raised outer coil. This seemingly minor detail enhances the concentric development and thus the precision of the balance spring. Beginning around 1860, Edouard Philips researched balance springs and their various shapes. His research, which he published in 1861, still remains valid today. The tables and graphics devised by this French professor of mathematics served as the indispensable basis for the shaping of subsequent balance springs. Because Breguet overcoil balance springs are quite costly to manufacture, they are now found only in very high-quality calibers.

Breguet Hands

A popular, very elegant and classical shape for watch hands. A circular hole is found at the terminal end (near the point) of a Breguet hand.

Bridge (Bar)

A specially shaped metal part in which at least one pivot of a moving part of a watch turns. A bridge is screwed at both its ends to a plate, where the opposite end of the pivot(s) is/are inserted. Bridges (also known as “bars”) are usually named after the rotating parts that they support, e.g. center-wheel bridge or barrel bridge.

Bridge Movement

The wheels of a watch movement are borne beneath individual bridges which are screwed to the bottom plate.

Barrel

The barrel consists of a toothed disk and a cylindrical box. The latter is usually closed by a cover. The barrel turns freely on its arbor. The mainspring is coiled inside the barrel. The barrel´s toothed disk meshes with the first pinion of the train of a mechanical watch.

Bearing

A hole drilled to accept a pivot of a gear train. In fine wristwatches and pocket watches, as well as in clocks, friction is reduced by inserting bearing jewels into the holes which accept the rapidly rotating pivots of wheels and pinions. Simpler timepieces make do with simple holes drilled into the plates, bridges, or cocks. This simpler solution, however, has the drawback that the pivot holes soon widen as a result of abrasion, especially if lubrication is insufficient. This shortcoming can be remedied by the insertion of bushes, which are usually made of brass or bronze.

Bezel

A term which can have a variety of meanings in horology. Strictly speaking, it signifies the ring snapped onto the middle of a watch case to hold the glass. Often, however, the same word is also used to describe a rotating (usually metal) ring affixed to the front of a watch’s case.

Brass

This alloy of copper and zinc is an important metal used in watch manufacturing. Depending on the purpose to which it will ultimately be put (e.g. for use as a plate), brass alloys may contain varying amounts of their constituent substances.

Balance Spring Stud

A small piece of metal, pinned or (in modern movements) glued to the outer end of the balance spring. The balance spring stud is affixed (usually screwed) to the lug of the balance cock or plate.

Balance

A circular metal hoop which, together with the balance spring, embodies the regulating organ of a mechanical watch. It has a decisive influence on the precision of the watch’s rate. The balance can be defined as a statically poised “oscillating wheel”. Bimetallic balances were still used as late as the 1940s to compensate for temperature variations on precision watches. After the selfcompensating “nivarox” balance spring had matured to the point that it was ready for serial production in 1933, bimetallic balances gradually became less important. They were increasingly replaced by monometallic “glucydur” balances made from beryllium bronze. Combined with a nivarox balance spring, the glucydur balance was an ideal regulating organ which lost none of its importance in ensuing decades. This combination of nivarox balance spring and glucydur balance is currently used in nearly all high-quality mechanical watches.

Balance Spring

The balance spring can justifiably be described as the “soul” of a mechanical watch. The inner end of this spirally coiled spring is affixed to the balance staff; the outer end is affixed via the balance spring stud to the balance cock. The elasticity of the spring ensures that the balance swings regularly to and fro. In combination with the moment of inertia of the balance´s hoop, the active length of the balance spring determines the duration of each vibration of the balance. For this reason, most watches are equipped with an index which can be shifted in infinitesimal increments to finely change the active length of the balance spring. Lengthening the active length causes the watch to run slower; shortening the active length causes the watch to run faster. The precision of mechanical watches also depends on the quality of the material and the form of the balance spring. This spring is three or four times more slender than a human hair and weighs 2/1,000ths of a gram (0.002 g). Despite its extreme slenderness and feather-light weight, it is nonetheless capable of resisting tension equivalent to a weight of 600 grams. The slender coils of a balance spring annually contract and expand more than 200 million times.

Chamfering

Chamfered (beveled) edges on steel components are one attribute that distinguishes fine and very fine watches. Chamfering is either mechanically accomplished with the aid of so-called “pantographs” or, in luxury watches of the highest quality, the parts are beveled by hand: a watchmaker files the edges in the traditional manner. The ideal angle of the bevel should be precisely 45 degrees. Chamfering has no effect on the function of the movement.

Compensating Balance Spring

The elasticity of balance springs made of hardened steel varies with changes in temperature. This causes corresponding changes in the rate of a watch. To counteract this effect, precision watches are equipped with a bimetallic balance. Compensating balance springs were first marketed under the name “nivarox” in 1933. Nivarox, an alloy composed of several metals, enables the balance spring to compensate for changes in temperature. All of today’s better-quality wristwatches use nivarox balance springs in combination with monometallic glucydur balances.

Cesium Clock

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Chronograph

The word “chronograph” (or the etymologically more accurate term “chronoscope”) describes a watch with an hour hand and minute hand, as well as a (usually centrally axial or “sweep”) chronograph seconds hand. This last-mentioned hand is linked to a special additional mechanism which starts, stops, and returns the hand to its zero position, usually in response to pressing one or more buttons. The time display is unaffected by the activity of this mechanism. Depending on the specific version, a chronograph may also be equipped with counters to tally the minutes and hours which have elapsed since the stop-time function was switched on. Pressing the return-to-zero button causes all of the chronograph hands (including those on the counters) to return to their starting positions. Chronographs with two push-pieces have dominated the market since the 1930s. One of the two push-pieces starts and stops the chronograph hand; the other returns it to its zero position. Chronographs of this type make possible additive stopping, i.e. the chronograph hand can be repeatedly stopped and restarted from the position it reached the instant it was halted. Depending on the frequency of the balance, a mechanical wristwatch chronograph can stop time with up to tenth-of-a-second accuracy.

Chronometer

A precision watch which has proven the accuracy of its rate during a 15-day series of tests conducted at an official testing site (e.g. at the C.O.S.C. in Switzerland). To qualify as a chronometer, the watch’s average daily rate must not err by more than -4 or +6 seconds in each of the following five positions: crown left, crown up, crown down, dial up, and dial down. The average daily deviation of rate may not exceed two seconds; the greatest deviation of rate must not exceed five seconds. All candidate watches are tested at temperatures of 23.8 and 38 degrees Celsius. Only after having passed the chronometer tests does a watch earn the right to bear the word “chronometer” on its dial and to be sold along with an official rating certificate.

Cloisonné Enamel

Enamel which has been separated into varicolored compartments (so-called “cloisons”) by means of metal partitions which prevent the liquefied material from mixing. Gold wires measuring 0.007 mm in width and approximately one mm in height are bent into the desired shapes and affixed to the dial to create a motif. A specially trained craftsperson known as a “cloisonneur(e)” performs these tasks, the difficulty of which is inversely proportional to the size of the dial or motif. After the wires have been bent and affixed to create the finished motif, each of the tiny cloisons is filled with powdered enamel of the desired color. As many as five layers of this finely grained material must be applied with a goose quill. After each layer is applied, the piece must be fired in a kiln. The lower layer fuses with the uppermost layer to create a play of colors having many nuances. The gold wires protrude above the plane of the final layer of enamel, so the cloisonneur(e) must manually abrade them until they are flush with the surface of the enamel. This abrasion is followed by a final hand polishing.

C.O.S.C.

Contrôle Officiel Suisse des Chronomètres (Official Swiss Chronometer Testing Site). A Swiss agency with headquarters in La Chaux-de-Fonds and subsidiaries in Bienne, Geneva, and Le Locle which conducts all official chronometer tests and issues the corresponding rating certificates. The acronym “COSC” has been in use since 1973.

Counterfeits

The counterfeiting of watches was already a serious issue long before the Far East became a destination for mass tourism. Abraham Louis Breguet (1747–1823) used a secret insignia in his effort to protect himself against the unauthorized misuse of his name. Renowned watch companies exert rigorous efforts to counteract counterfeiting, but the ongoing struggle against imitators seems nearly hopeless. Like the fabled Hydra, each destroyed counterfeit seems to spawn two new ones. Modern fakes are more-or-less accurate copies of common watch models. They primarily rely on the readily recognizable appearance of the authentic watch and/or the insignia of its maker. The quality of the imitation generally plays a subordinate role. The criminal energy is directed less towards the fake´s buyer, who usually knows what he is getting for his typically small sum of money. Damage is suffered by nearly all luxury brands. Certificates, invoices, and carrying cases no longer serve as guarantors of authenticity because these items too are readily and frequently counterfeited.

Case

The protective outer housing of a watch. Cases are made in a vast array of different versions and from a wide range of materials. A distinction is drawn between open (Lépine) cases and closed (hunter) cases on pocket watches. Cases which are protected against spray or fully watertight to various depths are frequently used on wristwatches. There are also a large number of different case shapes (round, square, oval, rectangular, tonneau shaped) and materials (platinum, gold, silver, steel, titanium, aluminum, plastic, etc.).

Crystals

Various sorts of crystals are used on wristwatches. Glass crystals are primarily found on early wristwatches. These crystals are scratch-resistant, but very fragile and prone to shattering. Beginning in the 1940s, glass crystals were ever more frequently replaced by man-made plastic crystals (Plexiglas). These are unbreakable, but prone to scratching. Mineral crystals have a hardness of 5 on the Mohs’ scale and are therefore significantly more robust than Plexiglas crystals. Today’s high-quality wristwatches primarily rely on synthetic sapphire for their crystals. This material, which has a hardness of 9 on the Mohs’ scale, is extremely resistant to scratching, but can only be processed with special diamond-tipped tools.

Cadrature

Technical term used to describe the additional governing mechanism added to a complicated watch: for example, the mechanism for a chronograph, repeater striking-work, or calendar. Depending on the construction, a cadrature can be either integrated into the movement or mounted on a separate plate and connected in an additive manner to the main movement. The latter, the so-called “modular” solution, is usually less costly because its makers can rely on a readymade movement. Integrated constructions, e.g. for chronographs or repeaters, must be individually developed. Nearly all additional functions are now available in modular form.

Caliber

The dimensions and form of a movement and its parts. The name and/or number of a caliber makes it possible to exactly identify the device, for example, when ordering replacement parts. As late as the 1970s, large ébauche manufacturers sometimes had more than 100 different calibers in their palette of products. This wide diversity no longer exists for calibers. Distinctions has traditionally been drawn between round calibers for open-face watches (Lépines), round calibers for sprung cover watches (Savonnettes or hunters), and various shaped calibers (e.g. baguette-shaped, tonneau shaped, oval or rectangular calibers). Lépine calibers are recognizable by the fact that the staff which bears the seconds hand is situated along an imaginary line extended from the winding stem. This differs from the situation in hunter watches, in which the staff bearing the axis of the seconds hand, the center of the watch, and the winding-stem form a 90° angle. If a small seconds subdial is present, it is located at the “6”. Readymade ébauches provided by ébauche suppliers should be distinguished from so-called “manufacturers” calibers. The latter are movements which manufactories produce for their own use. Finally, one sometimes encounters the term “reserved” calibers. This refers to ébauches which ébauche makers develop and/or produce exclusively for individual clients. Other établisseures have no access to these calibers.

Calotte

The French word “calotte” means “skullcap”. In watchmaker’s parlance, it describes a steeply domed case or the domed front part of a wristwatch’s case.

Carat

A unit of measure used to express the fineness of gold. So-called “fine gold” is nearly 100% pure and is synonymous with “24-carat gold”. If, for example, the case of a wristwatch is made from 18-carat gold, then the alloy contains 750 parts gold for every 1,000 parts of alloy. The remaining one-fourth of the alloy consists of other metals (copper, brass, silver, etc.). Fourteen-carat gold has a fineness of 585 parts per 1,000. Eight-karat gold has a fineness of 333 parts per 1,000. The fineness of the alloy is shown on the watch’s case as a hallmark punched into the metal.

Cocks

Unlike a bridge (or bar), a cock is screwed to the plate at only one of its two ends. The other end of the cock “floats” freely. Examples of cocks include the balance cock, escape wheel cock, etc.

Coaxial Escapement

An escapement for mechanical watches invented by English master watchmaker George Daniels. Thanks to a thoroughgoing redesign of the impulse-providing elements, the resultant friction, which cannot be entirely eliminated, is significantly reduced, thus making it possible to do without lubricant oil. This, in turn, avoids the deleterious effects on the amplitude of the oscillating system that are caused by the viscosity of liquid lubricants. Intervals between servicing can be markedly lengthened. Unlike conventional escapements (pallets, escape wheel), the coaxial escapement consists of three components: an intermediate wheel, a coaxial wheel, and a pallet with three pallet jewels. As in a conventional lever escapement, here too the roller table is affixed to the balance staff. But unlike the roller table of an ordinary escapement (which has only one roller-jewel), the roller table of a coaxial escapement also has an impulse pallet. The name “coaxial escapement” derives from the fact that a single staff serves as the axis shared in common by the escape wheel and the large escape wheel pinion (with its wolf teeth, which mesh with the teeth of the intermediate wheel). As far as the functioning of the entire ensemble is concerned, suffice it to say the following: when the balance turns clockwise, it receives a direct stimulus from the escape wheel to the impulse pallet of the roller table. Only when the balance turns counterclockwise does the pallets proper come into play. A tiny impulse is given by the escape wheel pinion to the middle impulse pallet on the pallets. After each impulse, the escape wheel is briefly halted by the outer pallet jewel so that the balance can continue to freely swing in the same direction.

Compensating Balance

Temperature variations deleteriously affect the rate of a mechanical watch because they alter the elasticity of steel balance springs. Rising temperatures cause a watch to lose rate; falling temperatures cause it to gain rate. More than 200 years ago, English watchmaker John Arnold invented the bimetallic slit compensation balance rim, which partly compensated for the not insignificant errors that temperature variations caused in the steel balance spring. As its name explicitly states, this component consists of a bimetallic hoop made of two conjoined metals (e.g. steel inside and brass outside). Brass has a higher expansion coefficient than steel. When temperatures rise, the brass expands more than the steel so that the free ends of the slit brass hoop shift position towards the balance staff. This compensates for the elongation of the steel balance spring. When the temperature falls, the balance’s rim has the opposite effect. Compensation balances are more costly to manufacture and more elaborate to assemble than ordinary balances, so they are used only in better-quality watches. The balances of cheaper movements lack this compensating ability, so the rate of cheaper movements is more drastically affected by variations in ambient temperature.

Complication

An additional mechanism in a mechanical watch. The most important complications include: automatic winding systems, equation-of-time displays, chronographs, as well as flyback, perpetual calendar, repeater movements, automatically chiming works (grande/petine sonnerie), tourbillons, and alarms.

Crystal Glass

Colorless glass. Glass was used as a material to protect the dials of watches until the 1940s. The problem with glass crystals is that they are prone to breakage. Even a slight blow against the crystal is apt to shatter the fragile glass pane.

Crown

A usually grooved button which can be twisted to wind the mainspring, set the hands, and/or adjust the date display. The crown was also sometimes used to govern the chronograph function on older watches. On modern watertight watches, the crown can frequently be screwed to the case. A severe lateral blow to the crown can cause it to break off, so the rims of the cases of modern sport wristwatches usually protrude slightly on either side of the crown to protect the crown against damage.

Crown Winding

Until the late 19th century, small keys were used to wind the mainsprings and/or set the hands of many pocket watches. A watch with a modern crown-winding system relies on a small crown to accomplish both of these tasks. Which task the crown performs depends on how far it has been extracted from the case. The crown winding system in common use today was devised by Jean Adrien Philippe, who received a patent for his invention on September 7, 1861. Philippe’ idea involved a transmission wheel, which was mounted on the winding stem in such a way that this wheel can rotate. This wheel is coupled via a gear cut with wolf teeth to the hand-setting pinion, which can be shifted back and forth. The convenient “empty” backwards rotating of the crown was an improvement which perfected the crown-winding system. Nowadays, this winding system is found on many millions of hand-wound and self winding watches.

CET

Central European Time. Germany and other countries in Central Europe instituted Central European Time on April 1, 1893. Central European Time is one hour ahead (+1) of World or Universal Time (also known as GMT or Greenwich Mean Time). GMT is defined as the mean solar time at the Greenwich meridian (0° longitude).

Coin Watch

A coin with a built-in watch movement. The first coin watches were constructed in the 18th century. To create such watches, a coin is halved, then each half is hollowed out and an ultra-flat movement is inserted “sandwich style” between the coin´s halves.

Cleansing

A mechanical movement performs very arduous work, so it ought to receive qualified servicing at Wempe Jewelers at least once every four years. It goes without saying that an automobile, the parts of which are in motion only a few hours each day, receives an oil change and servicing at regularly scheduled intervals. The parts of a watch, by comparison, are in motion 24 hours a day. Failure to give a watch regular servicing can result in damage to the delicate components of the watch’s gear train. When a watch is given to Wempe for servicing, qualified watchmakers completely disassemble the movement, thoroughly check every part, then reassemble the watch.

Chablon

There is no English equivalent for this technical term in French watchmaker’s parlance. It denotes a set of unassembled components for a movement blank.

Column Wheel Cronograph

Without an intelligent governing mechanism, it would not be possible to start, stop, and return to zero a chronograph’s seconds hand independently of the movement. Classical chronograph calibers rely on a pivoting column wheel to govern these three functions. Depending on the details of the movement’s construction, this comparatively elaborate component may have five, six, seven, eight, or even nine columns. Each time one of the chronograph functions is triggered, the column wheel progresses clockwise through a precisely defined angle. If the end of a rocker comes to rest atop one of its columns, the latter keeps the former in a raised position. If the rocker comes to rest between two columns, gentle pressure from a spring keeps it in a depressed position.

Center-of-Gravity Error

In theory, it should always be possible to create a perfectly poised assembly consisting of the balance and its balance spring. In practice too, near perfection is not unattainable. Perfection can be approached by adjusting the weight screws on the balance’s rim, or by milling grooves or drilling holes in the rim. But the pleasure derived from this elaborate “balancing act” is only short-lived because sooner or later the center of gravity almost always strays away from the center of the balance assembly. This results in center-of-gravity errors which affect the rate of a mechanical watch held in a vertical position.

Central Seconds (Sweep Seconds)

A seconds hand whose axis is situated in the center of the dial. On watches with central seconds, the arbor of the center wheel is hollowed out to provide space for the staff onto which the seconds hand is perpendicularly affixed. A distinction should be drawn between movements with direct central seconds and those with indirect central seconds. The former lies within the flow of energy of the gear train; the latter lies outside the flow.

Cylinder Escapement

The cylinder escapement was invented by English watchmaker George Graham about 1726. This type of escapement is found in early wristwatches. If it is used in a more recent wristwatch, its presence there suggests that this watch is simpler and less costly. The cylinder escapement dispenses with the pallets as a connective link. Instead, the teeth of the escape-wheel penetrate directly into a hollow cylinder, which simultaneously serves as the balance staff. Because of the inadequately accurate rate of movements that rely on this type of escapement, the cylinder escapement is no longer used in contemporary watches.

Date Display

The date can be shown either in analogue fashion by a hand or digitally by numbers printed on a disk. The date hand or disk rotates around its own axis once every 31 days, advancing through one increment on or about midnight of each successive day. On a hand-type date display, the numbers 1 through 31 are printed on the dial and the tip of the designated hand points to the current date. Wristwatches with digital date displays have a date disk affixed atop the front side of the movement. The number corresponding to the current date appears inside a little aperture cut into the dial. A magnifying lens integrated into the crystal enhances the legibility. A distinction should be drawn between “creeping“ and “jumping“ date displays. The former are smoothly and gradually advanced by the watch’s movement. The latter continually sap energy from the movement during the course of the day and store that energy in a spring, which unleashes its reserve of energy precisely at midnight, causing the date display to leap forward by one increment. Date displays can have either a single ring, two disks, two concentrically arranged and numbered disks, or one circular and one cruciform disk. In the last-mentioned variant, the circular disk bears the digits in the “ones“ column and the cruciform disk bears the digits (and the blank space for single-digit dates) in the “tens“ column to indicate the date. These “big date“ displays are larger and hence more readily legible than smaller displays with only one window.

Dateline

According to an international agreement, the dateline nearly coincides with the 180th meridian of longitude, which traverses the Pacific Ocean near New Zealand and the Fiji Islands. A westbound traveler who crosses the dateline “loses” a day and jumps ahead to the day and date after tomorrow. An eastbound traveler who crosses the dateline “gains” a day and repeats the same day and date a second time. This procedure compensates for the differences in dates and days of the week that arise in the course of a circumnavigation.

Digital Time Display

Depiction of the time by means of numerals. Digital indicators for the hours, minutes, seconds, and/or date were already in use before the invention of quartz timepieces. Digital displays on mechanical timepieces consist of appropriately printed, rotating rings or disks. Digital time displays on quartz wristwatches initially used light-emitting diodes (LED), but these used too much electricity so they were soon replaced by liquid-crystal diodes (LCD).

Double-sided Watch

A watch with one dial on the front and another on the back side. Double-sided pocket watches are much more common than double-sided wristwatches. Modern double-sided wristwatches are available, for example, from Jaeger-LeCoultre (“Reverso Duo-Face”) and Patek Philippe (“Sky Moon Tourbillon”).

Double Movement

A timepiece with two completely separate (hand-wound, automatic, or quartz) movements which can be used, for example, to show the times in two different time zones. The chief problem associated with wristwatches that have double movements, and especially with mechanical models, is that the two movements can stray out of synchrony as a result of differences in their rates.

Doublé (Plate, Plating)

The French verb “doubler” means “to double”. At first glance, watches with doublé cases appear to be more valuable than they actually are. A usually nonprecious substrate is plated with a more or less thin coat of precious metal, e.g. by pressing the precious metal layer onto the substrate in a hydraulic press. If the precious metal is gold, the result is called “rolled gold plating”. In addition to gold, other precious metals such as silver or platinum can also be used as plating. The thickness of the precious metal coating is measured in microns (thousandths of a millimeter). Twenty microns means that the precious metal layer is 20/1,000ths or 2/100ths of a millimeter thick. One disadvantage associated with plated wristwatches is that the precious metal coating gradually wears off. The rate at which this occurs depends on how often the watch is worn and how much perspiration it is exposed to. The backs of plated watches are frequently made of sturdy stainless steel.

Display of the Age of the Moon

An indicator showing the number of days which have elapsed since the most recent full moon. In a synodic month, the interval from one new moon to the next is exactly 29 days, 12 hours, 44 minutes, and 3 seconds in duration. Typical moon-phase displays consist of a disk, cut around its periphery with 59 teeth, and having two full moons printed or painted diametrically opposite each other on its surface. Powered by the movement, this disk requires two lunations to complete one full rotation around its own axis. The current phase of the moon can be determined by peering through a specially shaped aperture cut into the dial. A correspondingly subdivided scale surrounds the periphery of the moon-phase display. Moon-age displays deviate from astronomical reality by about eight hours per year. In addition to these simple versions, more complex constructions have also been devised: these reduce the error to just a few minutes per year.

Diver’s Watches

A wristwatch that is worn while swimming or scuba diving should have a case that is watertight to at least 100 meters. But according to German industrial norm no. 8306, a diver’s watch must also meet other criteria. In addition to its watertightness and good legibility, it must also have a mechanism (for example, a bezel that rotates in one direction only) which enables the wearer to preset the duration of a dive. The legibility is also strictly defined. The time of day, the preset dive time, and the watch’s functions must be unmistakably legible from a distance of 25 centimeters in total darkness. Professional diver’s watches must be watertight to at least 200 meters. Furthermore, their impermeability to water should be tested at yearly intervals. A diver’s watch which meets all of these criteria may bear the DIN (German industrial norm) mark. For their own safety, divers should have the watertightness of their watches tested twice yearly by Wempe Jewelers.

Dial Train (Motion Work)

A gear train situated between the plate and the dial. It transmits and translates the rotation of the minute pinion to the hour hand. Furthermore, in combination with the hand-setting system, the dial train makes it possible to exactly reset the positions of the hour hand and minute hand after the crown has been partially extracted.

Equation Display

Because of the elliptical shape of the Earth’s orbit around the sun and because of the tilt of the Earth’s axis, the difference between the year’s shortest and longest solar days amounts to 30 hours and 45 seconds. Keeping time according to true solar time with its continuously changing day lengths would be impractical in daily life, so astronomers defined “mean solar time”. The length of a mean solar day (86,400 seconds), which is indicated by all ordinary clocks and watches, is calculated by averaging the lengths of all of the true solar days in one year. The equation display, which was invented in the late 17th century and which has since become extremely rare, depicts the difference between mean solar time and the true solar time. The maximal deviations occur in mid February (+14 min. 24 sec.) and early November (-16 min. 21 sec.). The lengths of the true and mean solar days are identical four times each year (on April 16, June 14, September 1, and December 25). The daily differences are programmed into the circumference of a kidney-shaped cam that annually completes one rotation around its own axis. An elaborate mechanism “reads” this cam and transfers the information to an additional minute hand or second pair of hands on the dial’s equation display.

Eight-day Movement

A specially constructed mechanical clockwork that provides a minimum of 168 hours or one week of power reserve. The “Hebodmas” (the name means “seven days”), which debuted in 1913 had a large barrel that covered the entire surface of its movement. Long-running, shaped movements from the 1930s had normal-sized barrels, but their gear trains were augmented with two additional intermediate wheels. An eight-day movement is an unusual and special feature for domestic clocks and other larger timepieces. Interesting wristwatches with long-lasting power reserves again became available around 1990. To help their owners remember to wind them, these mechanical marathon runners are typically equipped with power-reserve displays.

Endstone (Jewel Cap, Cap-jewel)

An undrilled jewel, flat on one side and domed on the other. The flat side of the endstone is placed on the balance jewel in order to limit the vertical play of the balance staff. The bearings for balance staffs are usually equipped with endstones. In very high-quality calibers, endstones are also used for the bearings of the pallet staffs and escape wheels.

Energy

The potential to accomplish work. Potential energy is required to power the gear train of a watch. In a mechanical clock, the source of this energy can be a tightened mainspring (spring power) or a raised weight (gravity power). The electrical energy required by a quartz timepiece can be supplied by an accumulator, a battery, or a capacitor.

Eternal Calendar

See perpetual calendar.

Escapement

A mechanism which incrementally conveys energy from the mainspring to the oscillating systems (balance and balance spring) of a timepiece and prevents the gear train from racing ahead unchecked. Among its other components, the escapement consists of the escape-wheel with its pinion and the pallets with its twin pallet jewels and fork. The majority of today’s high-quality wristwatches rely on a Swiss lever escapement. This name derives from the specific form of the pallets and the geometry of the escapement system, which was invented in Switzerland. The escapement of a mechanical wristwatch performs very arduous labor. If the balance’s frequency is 28,800 beats per hour, then the escapement allows the gear-train to advance in 691,200 individual increments each day. After four years have elapsed, this amounts to more than a billion impulses and exceeds the work of a human heart sixfold.

Ébauche (Movement Blank, Incomplete Movement)

French term for “sketch”. In watchmaker’s parlance, the movement blank of a watch is described as an “ébauche.” A functional movement consists of a movement blank, an escapement, a hoop-shaped balance and its spirally coiled balance spring, a mainspring, a dial, and hands. An ébauche is a complete movement (plates, bridges, gear train, steel components) lacking an escapement, balance, balance spring, mainspring, dial, and hands. Depending upon the specifications of its recipient, ébauches are currently available either with or without pressed-in jewels. The French word chablon, for which no English equivalent exists, is sometimes used in the context of movement blanks. A chablon is a set of unassembled components for an entire caliber or for various parts of a caliber. Blank movements are manufactured by specialized companies (e.g. Eta, Nouvelle Lémania, Frédéric Piguet).

Émail (Enamel)

“Émail” is the French word for “enamel”, a vitrifiable substance which can be given various colors and fused onto the surface of metals, either to protect or decorate the substrate. Enamel consists of silicious sand and calcium fluoride to which lead oxide, borax, and soda are added. The mixture is first melted at 1,200 degrees Celsius, then flash-cooled. The resulting granules are ground to a powder together with coloring agents, which include: antimonies, zirconium oxide, or titanium dioxide for white enamel; cobalt oxide, chrome oxide, or other colorants for colored enamel. Layers of enamel are either brushed or sprayed onto the cleansed metal substrate, or else the entire metal piece is dipped into the enamel. Afterwards the coated piece is fired in a special kiln at a temperature between 800 and 900 degrees Celsius. The enameling technique has been used on the dials and cases of watches for more than 350 years. During the first decades of the 20th century, enameled dials were practically standard equipment on fine wristwatches. Partly because of the expenses involved in their manufacture, enamel dials have become rather rare during the past few decades.

Établisseur

The French term “établisseur”, for which there is no English equivalent, denotes a watchmaker who buys components (movements, dials, hands, cases, etc.) from specialized manufacturers, then further processes and assembles these components to produce complete timepieces.

Flyback Chronograph

A special mechanism controls two chronograph seconds hands which are situated one atop the other, thus making it possible to simultaneously time two or more events which begin at the same moment (e.g. the individual finishing times of sprinters who all began a footrace at the same instant). A complex additional switching mechanism couples the flyback hand with the chronograph seconds hand. A special push-piece halts the flyback hand so that an intermediate time can be read while the chronograph seconds hand continues to move in the plane below the flyback hand. When this same push-piece is depressed again, the flyback hand rejoins its companion. Genuine flyback chronographs debuted in 1883. Wristwatches with flyback chronographs were first sold in 1920. Because of the elaborate and thus very costly technology inside them, such watches have always been very special items.

Factory Mark

Alongside the insignias which spell out their names, many watch companies and ébauche makers also used and continue to use a so-called “factory mark”. This mark, a readily recognizable logo, can be placed onto various locations on a watch movement. It is frequently found on the front side of the plate in a location which is ordinarily covered by the dial. Manufacturers of movement blanks sometimes also place their factory marks (along with the caliber number) beneath the balance near the balance cock. Cases generally bear the factory mark on the inner surface of the back. Some manufacturers eternalize their logos on the exterior of the watch, e.g. on the crown, back, and/or dial.

Facet

The steel and brass components of very fine watches have faceted edges (chamfering). The bevels on the edge of the part should ideally form a 45° angle.

Fineness

The ratio between the weight of the precious metal (e.g. platinum, gold, or silver) in an alloy and the total weight of the alloy. Nowadays, fineness is expressed in thousandths or in carats. Pure gold is 1,000/1,000 or 24 carats. The value of a carat amounts to 1/24th of the total weight: 1,000 divided by 24 equals 41.666. Fourteen carats thus corresponds to 585/1,000. Eighteen carats corresponds to 750/1,000.

Fine Adjustment

A mechanism used to make very slight alterations in the position of the index (or regulator). A large number of different constructions can be used to accomplish fine adjustment in mechanical watch movements. Swan’s neck fine adjustment is among the most exclusive of such mechanisms. A system which relies on an eccentric screw is far more common. A widely held but erroneous belief insists that a fine adjustment mechanism necessarily goes hand in hand with greater precision. Watches can be adjusted with a high degree of exactness simply by carefully positioning the ordinary tail of the index, although this operation requires extreme care and dexterity.

Fine Regulation

The elimination of as many factors as possible which may exert negative effects on the rate of a watch or clock. The degree of fine regulation depends upon the standards of the timepiece’s manufacturer and thus has an effect on the price of the finished product.

Finishing

The final work of assembling the parts of a watch and putting its case into working order.

Flat Balance Spring

Christian Huygens invented the flat balance spring in 1675. The spring’s points of attachment to the balance staff (collet) and balance cock (stud) both lie in the same plane as the spring itself. Unlike Breguet overcoil balance springs, flat balance springs have the disadvantage that they do not develop absolutely concentrically while they expand and contract. This can have a negative effect on the rate results. Modern mechanical movements usually have flat balance springs which have been given a special deformation to counteract the aforementioned shortcomings.

Frequency

Number of oscillations per unit of time, expressed in hertz (Hz). Most stationary clocks primarily rely on a pendulum as their rate-regulating organ. Portable timepieces are typically equipped with a balance. Both organs oscillate at a particular frequency. The pendulum of a seconds-pendulum clock requires exactly one second to complete the arc from one turning point to the other, so it has a frequency of 0.5 Hz or 1,800 beats per hour (A/h). Early balances increased the frequency of oscillation to 7,200 or 9,000 beats per hour. The frequency of the balances of pocket watches was first raised to 12,600 and later to the typical standard of 18,000 beats per hour (2.5 Hz). In wristwatches too, this latter balance frequency became the norm. To enhance precision, some watch manufacturers further increased the balance´s frequency to 21,600 A/h (3 Hz), 28,800 A/h (4 Hz) or even 36,000 A/h (5 Hz). However, balances that oscillate at higher frequencies also require more energy than slower-paced balances. Furthermore, as rotation speeds and centrifugal forces increase, considerable lubrication-related problems arise. Modern quartz clocks oscillate at a frequency of 32,768 Hz.

Flyback Hand

See chronograph rattrapante.

Full Calendar

A complete calendar with displays for the day, date, and month. Manual resetting of the date and month display is necessary at the end of months which have fewer than 31 days. Some wristwatches with full calendars automatically advance the month display at or near midnight on the day when the date display has reached the number “31”.

Geneva Quality Hallmark

A law passed on December 6, 1886 to regulate the voluntary monitoring of pocket watches forms the legal basis for the so-called “Geneva Quality Hallmark” or “Poinçon de Genève”. It stipulated strict standards of quality for the manufacture of watches in the Canton of Geneva. This regulation was made considerably more rigorous in 1957. From that year onwards, watchmakers who wanted their watches to bear the coveted hallmark were required to uphold 11 quality standards. The accuracy of a watch´s rate also occupied the focal point of interest. Wristwatches with movements measuring 30 mm or less in diameter had to undergo an 18-day testing program. Only if the movement fulfilled all of the criteria did it qualify to bear the “Poinçon de Genève”. The most recent version of the regulation dates from December 22, 1994. Preconditions for receiving the Geneva Quality Hallmark are the numbering and the submission of all candidate movements to the “Office for the Voluntary Monitoring of Geneva Watches”. The principal contents of the regulations involve the determination of twelve criteria related to the level of quality of all components and their processing. Among other details, steel parts must have polished edges and satin-finished front surfaces. The heads of screws must be polished or circularly grained; the slits in the screws’ heads must be chamfered. Other stipulations specify details about the jewels, gears, arbors and pivots, the affixing of the balance spring to the balance cock, the technical execution of the all-important oscillating and escapement system, the care taken in the crafting of the winding and hand-setting organs, and the labor which must be devoted to the making of the movement’s other components. Unlike the text of the 1957 law, the current regulations no longer stipulate minimum standards for the precision of the rate of submitted movements. Then as now, however, candidates for the Geneva Quality Hallmark must be assembled and adjusted within the territory of the Canton of Geneva.

Geneva Waves (Code Genève)

A commonly seen, rib-shaped embellishment given above all to the bridges and cocks of fine calibers. Geneva waves are applied before the components are galvanically ennobled, but remain visible even after that treatment. Geneva waves are generally found only on high-quality movements.

Glucydur Balance

The glucydur balance is a modern balance which replaced bimetallic compensating balances in high-quality watches after the invention of the compensating balance spring. Glucydur balances are made of a copper alloy which contains an admixture of approximately 3% beryllium. Glucydur can be recognized by its golden color. The simpler nickel balances, on the other hand, have a silvery hue. Glucydur balances have a hardness of 380 Vickers; nickel balances have a hardness of 220 Vickers; brass balances have a hardness of 180 Vickers. The greater hardness of glucydur balances makes them better suited for riveting, poising, and fine adjustment.

GMT

Greenwich Mean Time. Synonyms are World Time or Universal Time Coordinate (UTC). The prime meridian, i.e. zero degrees longitude, passes from north to south through the center of the GMT time zone. The mean time at the observatory in Greenwich, England is used as the standard for navigational purposes and international radio communications.

Gold

A precious metal with a specific gravity of 19.5. Gold having various degrees of fineness is used for jewelry and watch cases. In very fine mechanical watches, gold may also be used as the material for the regulating screws on the rim of the balance, for the jewels’ settings, for the wheels, or even for the entire movement.

Gold-filled

A coating of gold applied to a non-precious substrate material, e.g. brass.

Grande Complication

Highly complex pocket watch or wristwatch equipped with one or more of the following functions: chronograph, perpetual calendar, minute repeater, etc.

Grande Sonnerie

A large striking mechanism which, depending on its specific version, automatically sounds an audible signal to announce the arrival of full, half, and quarter hours. A second barrel is integrated into the movement to power this mechanism. As a rule, timepieces with grande sonnerie also have a slide-piece that can be shifted to shut off the audible mechanism. The grande sonnerie is frequently combined with a repeater movement.

Gregorian Calendar

After many years of preparation, and immediately after the wholesale cancellation of ten entire days, a calendar reform ordered by Pope Gregory XIII went into effect in Rome on October 15, 1582. This reform eliminated the tiny residual error contained in the Julian calendar, which had been in effect since 45 BC and according to which the year was too long by a fraction of a day: 0.0078 x 24 hours = 673.92 seconds too long, to be exact. The Gregorian calendar compensates for this slight error by dropping three leap years every 400 years. Whenever a secular year (i.e. a year whose last two digits are “zero”) which is not divisible by 400 arrives, that year is not a leap year. Hence, there will be no February 29th in the years 2100, 2200, and 2300 AD.

Guilloché (Engine Turn)

To engrave, with the help of a rose engine, a watch’s case or dial with a decorative pattern of slender, sometimes artfully crossing or interlaced lines.

Gyromax Balance

Early in the 1950s, watchmakers at the house of Patek Philippe discovered that the new glucydur balances, which no longer needed inertial weight screws on their rims, could be built in larger diameters without significantly increasing their weight. Larger diameter went hand in hand with an increase in the balance’s moment of inertia, which led to improvements in a watch’s rate performance. Patent protection was granted to the “Gyromax” balance on December 31, 1951. On this type of balance, eight slit, disk-shaped, regulating elements are borne on axially arranged pins. The elements can be rotated. This outstanding development can be seen as the precursor to the modern annular balance, which has no screws. Although Patek Philippe too initially continued to rely on the familiar mechanism for making fine adjustments in the position of the index as a means of altering the frequency of the balance, the fact remains the precision-enhancing advantages of the “Gyromax” balance can only be exploited to their full potential in combination with a freely oscillating balance spring.

Gear Train

In a normal hand-wound watch, the gear train consists of five pairs of wheels with their accompanying pinions. The teeth along the periphery of the barrel mesh with the leaves of the center wheel’s pinion, which is affixed to the same staff that bears the center wheel. The center wheel’s teeth mesh with the leaves of the pinion of the third wheel. The third-wheel meshes with the pinion of the fourth wheel. The fourth wheel meshes with the pinion of the escape wheel. Energy flows through the escape wheel and the other parts of the escapement system, ultimately arriving at the balance, which is thereby kept in motion.

Gravity

The gravitational attraction of the Earth draws all bodies towards the center of the planet. The acceleration undergone by freely falling bodies is measured in “g”. The influence of gravity on the rate of a mechanical timepiece should not be underestimated. Especially in pocket watches, which are typically worn in a vertical position, gravity can cause significant disturbances in the rate behavior if the center of gravity of the balance is not situated exactly centered on the balance staff. Only if it is absolutely centered is there no point along the rim of the balance which is continually drawn towards the center of the Earth with greater force than all other points along the rim, thereby causing either acceleration or deceleration.

Half Perpetual Calendar

A watch that correctly indicates the various lengths of the months throughout one leap-year cycle. The 29th of February is unknown to them because they lack a wheel which rotates around its own axis once every four years.

Half Savonette (Half-hunter)

Watch with a sprung cover having a circular opening in its center through which the time can be read when the cover is in its closed position. This type of case was most common on pocket watches. Prior to the introduction of the first shatter-resistant watch crystals in the 1920s, half-hunter cases were sometimes also used on wristwatches. Half-hunter pocket watches usually had a pane of glass in the circular aperture; half-hunter wristwatches usually lacked this pane.

Hand-wound Watch

Timepiece whose mainspring requires manual winding.

Hectometer Scale (Production Counter)

The calibrations of a production counter help to determine the production capacity for identical pieces in a serially mass produced item. The chronograph is started at the beginning of the process leading to the production of a serially mass-produced piece, then stopped again when the process is finished. The hand on the dial shows how many pieces have been manufactured per hour. This assumes, however, that no more than 60 seconds are required to manufacture each piece.

Heures Sautantes (Jumping Hours)

A mechanism in which a disk, printed with a series of digits from 1 to 12, replaces the hour hand. The current hour is visible in digital form, i.e. it is displayed as a digit or digits. One and the same numeral is visible for 60 minutes through an aperture cut into the dial. After the minute hand reaches the “12”, this numbered disk jumps suddenly forward to display the next numeral, thereby indicating that the next hour has begun.

Hooked-tooth Lever Escapement

Another name for the Swiss lever escapement. The name results from the hooked shape of the teeth on the escape wheel.

Hallmark

A mark stamped onto the case of a watch to provide information, for example about the type and fineness of the precious metal, the country (and sometimes also city or canton) of origin, the year of manufacture, and the identity of the case’s maker. The trademark or logo of the company that made or delivered the watch, a reference number, and a serial number are also frequently punched onto the case.

Hunter

Watch whose case has both a back cover and a hinged, sprung, front cover to protect its crystal.

Hunter Caliber

A movement in which the fourth wheel and the crown form a 90° angle with the center of the watch. A small seconds subdial is located at the “6”.

Hour Counter

A detail in the construction of some chronographs, an hour counter tallies the number of hours which have elapsed since the beginning of a stop-time sequence. Most hour counters can tally a maximum of twelve hours. When the return-to-zero push-piece is depressed, the hand on the hour counter also returns to its starting position.

Incabloc

Incabloc, one of the most common and widely used shock absorption systems for mechanical watches, was first serially manufactured in 1933. It is generally acknowledged to be the most successful shock absorption system in the history of portable timepieces. Its success is due in part to the fact that this shock absorption system can be readily integrated into all calibers. The Incabloc shock absorption system is usually shaped like a lyre.

Incastar

Developed by Portescap, this adjustment system for mechanical watches does not need the typical index. The outer end of the balance spring is pinched between two elastic rollers. The position of one of these rollers can be shifted with the aid of a star-shaped component, thereby lengthening or shortening of the balance spring and altering the rate of the watch. This task would otherwise be accomplished by the index system, which is rendered unnecessary by the Incastar solution.

Indication

A display, e.g. of the time, date, day of the week, month, equation of time, power reserve, time in a second time zone, etc.

Indirect Central Seconds

On watch movements with indirect central seconds, the impulse for the seconds hand comes from outside the flow of energy passing through the gear train. For this reason, this type of seconds mechanism is frequently found on calibers which were originally constructed to support small seconds subdials and subsequently rebuilt to support a “sweep” seconds hand. Modern calibers are usually constructed to support a centrally axial “sweep” seconds hand. For this reason, they usually have direct central seconds, i.e. the impulse for the seconds hand is within the flow of energy passing through the gear train.

Inner Cover

An additional protective cover (dome or cuvette) beneath the outer back cover of a watch. This type of additional cover is most commonly found on pocket watches. Early wristwatches with hinged cases were sometimes also equipped with inner covers.

Independent Seconds (Seconde Morte)

The text of a patent granted to a movement with a jump-type seconds hand describes the independent seconds mechanism as “a mechanism for the step-by-step forward motion of the seconds hand on a gear-driven timepiece movement”. Essentially, this is nothing other than an ordinary mechanical caliber. On a watch whose balance has a frequency of 18,000 beats per hour, the independent seconds mechanism counts five vibrations, then releases the seconds hand, which (as on a quartz watch) leaps forwards by an increment of one full second.

Julian Calendar

The familiar cycle of three ordinary 365-day years followed by one 366-day leap year was initiated by Roman emperor Gaius Julius Caesar. The year was defined by the Julian calendar, however, is 0.0078 days longer than the actual astronomical year. Pope Gregory XIII corrected the error, which in the course of many centuries had accumulated to ten full days, by instituting the Gregorian calendar in the year 1582.

Jewel Hole

A cylindrically shaped synthetic gemstone (usually a ruby), with a hole drilled into its center. Jewels are pressed into plates, bridges, and cocks to reduce friction and minimize wear in the pivot holes drilled into planar components. The rapidly rotating pivots of a gear train spin inside the jewels. In very fine watches, the walls of the holes in the jewels are not cylindrical in shape, but are rounded into an olive-like shape, whence the technical term “olive” or “olive-cut jewel hole”. The rounding on the walls of the hole further reduces friction in the bearing because it minimizes the area of contact between the jewel and the pivot. Furthermore, an olive-cut jewel hole gives greater freedom of movement to the pivot.

Jumping Hours

See heures sautante.

Jeweled Pallets

Pallets fitted with ruby pallet jewels.

Jewels

To reduce friction in precise watches, gemstones are inserted at the critical points, for example on the impulse faces of the pallets and on the impulse pin (roller pin). Natural gemstones (e.g. rubies or sapphires) were used in the past. Nowadays most modern watches exclusively rely on synthetically manufactured jewels. One can distinguish among bearing jewels with holes, endstones (cap jewels), pallet jewels, and roller pins (impulse pins). Merely because a movement has a large number of jewels doesn’t necessarily mean that it is an especially high-quality movement. Just the opposite: the dial of a cheap wristwatch may boast that the movement contains a large number of “jewels”, which might lead an uninformed person to assume that this must be a high-quality watch.

Karussell

A device similar to a tourbillon. The karussel was invented in 1892 by a Danish watchmaker named Bonniksen as an alternative to the tourbillon, which is more difficult to make and significantly more costly. A tourbillon typically rotates around its own axis once each minute. The oscillation and escapement system inside the karussel describes a circular arc of 360° once every hour. Some karussels have a shorter orbital cycle. In addition to its slower speed of rotation, another essential difference between a karussel and a tourbillon lies in the propulsion of the rotating organ. A tourbillon is caused to rotate by the fourth wheel, which means that the rotations of the tourbillon cage are indispensable for the to and fro oscillation of the balance and thus for the function of the entire movement. If the tourbillon comes to a standstill, so too does the entire watch movement. A karussel is usually propelled by the third wheel. The watch therefore continues to run even if the karussel, which is usually crafted as a plate, should come to a standstill. Karussels were first built into wristwatches in 2001.

Keyless Watch

A watch whose mainspring is wound via the crown.

Lever Escapement

This is currently the most commonly used type of escapement in mechanical watches. It was invented circa 1710 by the English watchmaker George Graham (the so-called “Graham dead-beat escapement”) for use in large clocks. Beginning in 1757, Graham’s student Thomas Mudge progressively evolved the lever escapement so that it could also be used in pocket watches. Portable watches rely on various types of lever escapements. Their names vary depending upon the shape of the pallets and include: the English lever escapement (which has pointed teeth on the escape wheel), the Glashütte lever escapement, the Swiss lever escapement, and the pin-pallet escapement. The Swiss lever escapement undisputedly dominates the field nowadays. The pin-pallet escapement is rather rare and is typically encountered only in very simple, inexpensive movements.

Lapping

The surfaces or edges of watch components can be smoothed and polished with the aid of a lapping (or polishing) machine. This polishing enhances the visual appearance and the value of a movement.

LCD

Abbreviation for “liquid crystal display”. When excited by an electrical field, a film of liquid crystal refracts incident light. This attribute makes such crystals very useful for digital quartz watches. LCDs replaced LEDs in the mid 1970s. Rather than generating its own light, an LCD refracts light falling upon it. The advantages of this are: — less electrical current is used — the display is continually visible and needn’t be specially triggered first — good visibility is provided under diverse lighting conditions — the assembly requires no moving parts. In its simplest version, an LCD consists of two plates of glass, each of which is coated on its inner surface with a layer of electrodes. Between the two plates are nematic (threadlike) liquid crystals which have elongated molecules and a nearly parallel ordering structure. Liquid crystals undergo excitation when the electrodes are exposed to an electrical field. If no field is present, the coating is clear and transparent. When current flows through it, the coating becomes turbulent, refracts light, and appears cloudy.

LED

Abbreviation for “light emitting diode”. These opto-electrical elements were used in the 1970s to indicate the time on quartz watches. Because the display saps so much energy when lit, it was kept dark unless specially triggered by pushing a button. This shortcoming soon led to its obsolescence, and the LED was replaced by the LCD.

Lépine Caliber

In this form of construction for watch movements, which is named after French watchmaker Jean-Antoine Lépine, the wheels and the balance share a common plane and run on one side of the plate beneath the bridges and cocks. Furthermore, in a Lépine caliber, the winding cum setting crown, the center of the dial, and the axis of the seconds hand are all aligned along the same line.

Luminous Dial

Dial from which the time can be read during the night and without additional illumination. To accomplish this, the numerals or indices and the hands are filled with a luminous material. Just seven years after Marie and Pierre Curie’s 1898 discovery of radium, the Büchler & Co. quinine factory in Braunschweig, Germany, began to market luminous dials and hands for watches. Pure radium is highly radioactive, so this element is no longer used on luminous dials. Tritium, a radioactive isotope of hydrogen with an atomic weight of 3, has likewise become obsolete. Watches with tritium as their luminous material can be recognized by the words “Swiss Made — T” on the dial. In place of these radioactive substances, modern glow-in-the-dark dials rely on alternative substances which are non-radioactive yet nonetheless luminous, e.g. Super-LumiNova.

Ligne

A traditional unit used to measure the dimensions of watch movements. The ligne derives from the old French foot or “pied due roi”. A common diameter for circular movements is 11 lignes. Rectangular movements sometimes measure 8¾ x 12 lignes. One ligne is equivalent to 2.2558 millimeters. One French foot equals 12 inches or 144 lignes. A foot is abbreviated with a single apostrophe ('); an inch is abbreviated with twin apostrophes (''); a ligne is abbreviated with three apostrophes (''').

Lunation (Lunar Month)

During one lunation, which is equivalent to approximately 29.5 days, the moon progresses through one full cycle of its phases: i.e. from new moon, through first quarter, full moon, and last quarter, to the next new moon.

Leap Year

According to the Julian calendar, every fourth year has an extra day added to it at midnight, February 28. Because of this additional day (February 29), a leap year has 366 days, rather than the 365 days which comprise an ordinary year.

Maltese Cross

The trademark of Vacheron Constantin is shaped like a Maltese cross. A similarly shaped component is used to limit the extent to which the barrel can be wound. Together with a finger mounted on the barrel arbor, the Maltese cross compensates for the greatest differences in torque in the powering of mechanical watches and clocks with gear trains. This elaborate technique is only rarely used nowadays and is found only in especially fine watches.

Manufactory

According to the unwritten laws of watchmaking, a company that makes watches can only describe itself as a “manufactory” if it makes at least one ébauche (movement blank). The companies whose artisans assemble readymade ébauches to produce finished watches are known within the industry as “établisseures”. The small and elite circle of mechanical-watch manufactories currently includes, among other names, Audemars Piguet, Chopard, Roger Dubuis, Girard-Perregaux, Glashütte Original, IWC, Jaeger-LeCoultre, A. Lange & Söhne, Patek Philippe, Piaget, Rolex, and Zenith.

Mariage

In watchmaker´s parlance, the French word for “marriage” describes the compilation of many, usually authentic components taken from various and sundry watches to assemble one complete new watch. Well-made mariages are difficult to identify, but even successful ones significantly reduce the value of a timepiece.

Mechanical Gear Train Timepiece

A clock or watch powered by a mainspring or descending weight. The regulation of the rate of these timepieces is accomplished by a balance with a balance spring or by a swinging pendulum. The development of the mechanical gear train clock probably resulted from the mechanism used to propel planetaria, i.e. devices which depict the motion of the planets. The first such artifacts date from the late 13th century. The oldest mechanical gear train clock in German-speaking Europe is probably the clock in Strasbourg cathedral. This clock was completed in 1352. Functional gear train clocks first appeared in England towards the end of the 13th century.

Megahertz (MHz)

A unit of frequency denoting one million cycles per second.

Micron

One millionth of a meter or one thousandth of a millimeter. The thickness of the gold plating on doublé watch cases is measured in microns, which are abbreviated with the Greek letter mu (µ). Doublé used to be at least twenty microns thick. Nowadays five microns is a more common thickness.

Micro Rotor

A rotor, integrated into the plane of the movement, which automatically winds the mainspring of a self-winding watch. The motivation which led to the invention of calibers with micro-rotors was the desire to build very slim and thus very elegant self-winding wristwatches. Constructions that rely on old-fashioned hammer-type oscillating weights (which move only through an arc rather than completing a full circle) or which rely on central rotors, Universal Genève followed suit in 1958 with the slim “Polerouter”. Piaget presented the Caliber 12 Pl in 1959: just 2.3 mm slim, it was the world’s slimmest automatic watch. Patek Philippe’s classic Caliber 240, which is 2.4 mm slim, has a micro-rotor made of 22-karat gold. Chopard’s LUC 1.96 debuted in 1996: this manufactory caliber has twin barrels, is 3.3 mm slim (including its jump-type date display), and has a power reserve of approximately 70 hours. are both situated in a plane above the plane of the movement and are consequently thicker than micro-rotor calibers. Micro-rotor calibers have not won a very large share of the market, but have nonetheless become a fixed feature in watch technology. The pioneer of the micro-rotor was Büren Watch Co., which received a corresponding patent in 1954. Three years later, this company debuted its “Super Slender”, which was a mere 4.2 mm thick.

Minute

With the introduction of mechanical gear train clocks, the “civil” day was subdivided into 24 hours of equal duration. The word “minute” is derived from the Latin phrase “diminutiva pars”, which means “a diminished part of a whole”. The Babylonians pioneered the sexagesimal system, which is based on the number “60”.

Minute Repeater

Minute-repeater watches ring one or more chimes to audibly announce the hours, quarter hours, and the number of minutes which have elapsed since the last quarter hour. Their highly complicated movements usually have two hammers which strike against two gongs. Each full hour is announced by the hammer’s striking a corresponding number of blows against a bass gong. The minutes ring out from a higher pitched gong. Quarter hours are heralded by double strikes (treble bass). The first minute-repeater timepieces were crafted around 1750. They were and still are the crowing glory in the art of crafting repeater strike trains.

Minute Counter

Stopwatches and chronographs often have a counter to tally the number of minutes which have elapsed since the beginning of a stop-time sequence. Counters which tally up to a maximum of 30 or 45 minutes are most common. The latter are found, for example, on the chronographs used by the referees who officiate at soccer games. Other counters can tally a maximum of only 15 or as many as 60 minutes. When the seconds hand of the chronograph or stopwatch is returned to its zero position, the hand on the minute counter likewise returns to its starting position.

Midday

The measuring unit used for all civil timekeeping is the progress of the sun across the sky. True midday is defined as the moment when the shadow cast onto the ground by a vertical post is shortest.

Module

A construction group. Among their other applications, modules are used in many self-winding chronographs. They are typically mounted onto the front (dial side) of the movement. A friction coupling is usually used to link the module with the flow of energy moving through the gear train. Modular constructions can usually be recognized without opening the case by the date display, which tends to be deeper below the dial and usually has a magnifying lens integrated into the glass above it, and by the V-shaped arrangement of the push-pieces and crown. Modules are also found in calendar watches, primarily on models which have so-called “perpetual calendars”. In such watches, the entire calendar mechanism is mounted on its own plate, which is affixed to the dial side of the movement. Strike train modules also exist.

Moon Phases

As a result of cyclical changes in the positions of the sun, moon, and Earth, the moon appears to pass through four phases (new moon, first quarter, full moon, and last quarter) before returning to new moon. The time which elapses from one new moon to the next is approximately 29.5 days.

Mouvement

French watchmakers use this term to denote the movement of a watch.

Mysterieuse

French term for a watch which is as transparent as possible and in which neither the movement nor the means of propulsion are visible.

Movement Blank

See ébauche.

Mainspring

A mainspring is a long, elastic, spirally coiled, strip of steel. Mainsprings were first used to store energy for mechanical timepieces during the 15th century. A mainspring is coiled inside a barrel. The torque provided by a mainspring is greatest when it is fully wound. As the mainspring gradually slackens, its torque declines continuously, which has an ill effect on the rate of the watch. A watch with automatic winding regularly tautens its mainspring. This leads to a relatively constant level of torque and thus to a regular rate. Modern wristwatches generally use mainsprings made of “nivaflex”, a special alloy which can be used to make a mainspring lastingly elastic and highly resistant to breakage. The S-shaped “nivaflex” mainspring regularly releases its store of energy.

Nonmagnetic

A watch is nonmagnetic when it is protected against the deleterious effects of magnetic fields. To accomplish this, components which are most susceptible to disturbance by magnetism are crafted from materials which cannot readily become magnetized (e.g. balance springs made of elinvar or nivarox are used together with balances crafted from brass, nickel, or beryllium bronze). Furthermore, various nonmagnetic metals are also used for components such as the pallets, escape wheel, and roller (or roller table). Another option is to encase the entire movement inside an additional inner case crafted from a highly conductive alloy. This inner case prevents magnetic fields from building up inside it.

One-handed Watch

The earliest geared clocks were equipped with only one hand, viz. an hour hand. Abraham-Louis Breguet’s famous “Souscription” pocket-watch was a one-handed watch. The time can only be approximated by consulting the dial of a one-handed watch. Wristwatches of this kind are rare, but not wholly nonexistent.

Oscillating Weight

In a self-winding movement, the oscillating weight is a body that is free to rotate and connected with the barrel via a gear train. When the movement is in a non-horizontal position, gravity causes this weighty mass to fall towards the center of the Earth. The kinetic energy generated during this fall is transferred by a gear train to the barrel, where the mainspring stores it as potential energy.

Pallets

One of the most complex components in mechanical watches, the pallets are shaped like a ship’s anchor, whence their French name “ancre”. Usually made either of brass or steel, pallets consist of several components, including the lever, the pallet staff, the pallet stones, and the dart or guard pin. The purpose of the pallets is twofold: to convey energy from the gear train to the balance, thereby keeping the latter in oscillation; and to prevent the gear train from racing ahead and quickly exhausting the energy available to it from the barrel.

Push-piece

Organ by means of which a function can be controlled. For example, a push-piece can be used to unlatch the hinged cover of a hunter watch; to start, stop, and return to zero the seconds hand of a chronograph; to trigger the striking-work on some repeater watches; or to reset the time zone on a world time watch.

Precious Metal

The cases of wristwatches are usually crafted from precious metals such as gold, platinum, or silver. Gold is available in alloys having a fineness of 333/1,000 (8 carat), 375/1,000 (9 carat), 585/1,000 (14 carat), or 750/1,000 (18 carat). The admixture of other metals (e.g. copper) to the alloy alters the hue of the gold alloy. If gold is used as the material for the rotor of a self-winding wristwatch, then 21-carat, 23-carat, or 24-karat gold are the alloys which are most frequently used. The fineness of platinum is 950/1,000. The disadvantages of silver watch cases are that they are very soft and that they tarnish readily. Covering them with a layer of gilt (vermeil) effectively prevents tarnishing, but suffers from the same problem that besets doublé cases: sooner or later, frequent wear and exposure to perspiration abrade the coating and expose the substrate.

Precious Metal Control (Swiss)

A partial revision of the Swiss laws governing precious metals went into effect on August 1, 1995. The following fineness designations have been valid in Switzerland for gold, silver, and platinum ever since: Gold 333 585 750 916 999, Silver 800 925 999, Platinum 850 900 950 999. Palladium is recognized as a precious metal with the following fineness designations: 500 950 999. The minimum thickness for gold, platinum, and palladium plating was reduced from 8 to 5 microns. Ten microns is the minimum for silver plating. The quality designation “coiffe or” is permissible only for watch cases or bracelets with a gold plating measuring at least 200 microns in thickness. The passage of this law also drastically reduced the number of official hallmarks which can be punched into the surface of jewelry or watches after they have passed an obligatory check by the Swiss Precious Metals Control Authority. Prior to July 31, 1995, there were individual hallmarks for each precious metal and each fineness. After that date, there has been only one hallmark (the head of a St. Bernard dog) combined with numbers designating the degree of fineness.

Power Reserve

Additional running time supplied by stored energy in excess of the normal winding interval of a watch (24 hours). The power reserve typically varies between 10 and 16 hours. The motive force supplied by the mainspring decreases during this interval, which leads to a reduction in rate performance.

Power Reserve Display (Réserve de Marche)

An indication of the remaining reserve of power available to a mechanical movement. Power reserve displays were first used on marine chronometers because the running down of such a timepiece, and the consequent loss of the exact time on the high seas, could be disastrous to navigation — and to the mariners who depended upon accurate navigation. For this reason, each glance at the dial also kept a sailor informed about the mainspring’s momentary status. When automatic winding mechanisms began to make inroads into wristwatches, the powerreserve display again began to play an important role. It showed that the self-winding mechanism was functioning properly. Power reserve displays almost entirely disappeared from the market for many decades, but this additional function has again become quite popular in recent years.

Positions

Unlike pocket watches, which usually remain in a vertical orientation inside their wearer’s vest or trouser pocket, wristwatches are worn in many different positions, for example, “crown up”, “crown down”, “crown right”, “dial up” and “dial down”. Precise watches are therefore adjusted in each of these five positions.

Parachute

Abraham-Louis Breguet (1747–1823) used this word to describe a shock absorption system which he invented. To protect the delicate pivots of the balance staff, Breguet affixed the corresponding jewels in elastic steel arms.

Pedometer Winding

An automatic winding system which uses an oscillating weight which, like the swinging weight in a pedometer, rocks up and down when the person wearing the timepiece walks. A gear train conveys the kinetic energy to the mainspring. Pedometer winding is believed to have been invented by Abraham-Louis Perrelet of Le Locle, Switzerland, in 1770. The first wristwatches with this type of winding system were marketed in the 1920s, e.g. by Léon Leroy (1922) and John Harwood (1924). Pedometer winding was still used in a few wristwatches as late as the 1950s.

Perpetual Calendar

A calendar mechanism which automatically takes into account the varying lengths of the months and which will not require manual adjustment until midnight on February 28, 2100.

Perpetual

A synonym for automatic winding or self winding. The word is used, for example, in the name of the “Rolex Perpetual”.

Plaqué d'Or

Thin, galvanically applied layer of gold put onto the surfaces of watch cases that are made of non-precious metals. See also doublé.

Platinum

Very unostentatious and extraordinarily precious metal used in the manufacture of watch cases. Platinum’s high price results from its extreme rarity, as well as from the difficulties involved in mining, refining, and processing it. More than 300 kilograms of ore must be mined to recover one gram of platinum. Only 100 kilograms of ore must be mined to recover one gram of gold. Furthermore, the successful processing of platinum imposes exacting demands on a metallurgist. Platinum has the highest melting point of all precious metals: it melts at 1,773 degrees Celsius, compared to 1,063 degrees for gold and 960 degrees for silver. Platinum is also harder, tougher, and heavier than other metals used in jewelry, which means that special tools and manufacturing techniques must be used to work platinum. Finally, watch cases made of platinum usually have a fineness of 950, i.e. the alloy is 95% pure platinum. A platinum watch case weighs about 35% more than an identical case made of 18-carat gold.

Plate

Sometimes called “movement plate”, this term designates a metal plate which bears the bridges (bars), cocks, and other components of a watch movement. The dial train (motionwork) is found on the dial side of the plate. The entire gear train and barrel, as well as the oscillating and escapement system, is attached to the back of the plate beneath the bridges (bars) and cocks. In addition to the threaded holes which accept the screws, the plate is also drilled with holes for the feet and for the bearings of the gear train.

Poinçon de Genève

See Geneva Quality Hallmark

Precision

The ticking clock numbers among the world’s oldest and most precise mechanical machines. If a watch’s movement deviates during one day (86,400 seconds) from the official norm by 30 seconds (a rather large error by contemporary standards), then that movement’s arithmetical error would be 0.035%. In other words, its degree of accuracy would be an astounding 99.965%. Modern mechanical wristwatches are considerably more precise, especially if they have earned an official chronometer certificate. The deviation of rate here is less than 0.005%.

Precision Regulation Mechanism

For example, a swan’s neck with a finely threaded screw. The entire assembly is affixed to the balance cock, where it enables a watchmaker to shift the position of the index in minimal increments.

Precision Timepiece

Timepiece with lever or chronometer escapement, and assembled from high-quality components, including an oscillating system that is able to compensate for changes in temperature. Precision pocket watches and wristwatches require at least fifteen functional jewels.

Prototype

Derived from the Greek language, this term denotes an original pattern or a model that serves as an archetype upon which subsequent versions are patterned. A prototype is the first specimen of a watch and is typically crafted by hand before serial production begins.

Pulsometer

A labor-saving, specially calibrated scale along the periphery of a watch (usually a chronograph) for medical purposes. As its name explicitly states, a pulsometer is used to measure a patient’s pulse. Depending on the calibration of the scale, the user counts either 20 or 30 pulse beats after starting the chronograph. The chronograph is then stopped and the tip of the chronograph’s seconds hand points to the numeral on the pulsometer scale which corresponds to the patient’s pulse rate in beats per minute.

Pin-pallet Escapement

On a pin-pallet escapement, the role which would otherwise be played by pallet stones is played by steel pins which rise vertically from the plane of the pallet. These pins mesh with the teeth on the escape wheel.

Quartz Wristwatches

Electronic wristwatches in which an oscillating quartz crystal serves as the regulating organ. The frequency of 32,768 Hz has become today’s de facto standard. Because the rate-regulating organ oscillates very rapidly, quartz timepieces are more precise than mechanical ones. Quartz wristwatches were first marketed in 1968.

Quater-year Calendar

See “half” perpetual calendar.

Rotating Cage

A delicate cage, often made of steel. Titanium or aluminum are frequently used as the material for this assembly on modern wristwatches. On watches equipped with a tourbillon, this cage contains the oscillating and escapement system (which consists of the balance, balance staff, balance spring, pallets, and escape wheel). The cage rotates around its own axis, usually at a rate of one rotation per minute. A rotating cage should be sturdy, filigreed, and as lightweight as possible. Crafting this assembly numbers among the most challenging and most laborious of a watchmaker’s tasks.

Radio Timepiece

In 1978, a law about the determination of time (“time law”) was passed in Bonn which commissioned the Physikalisch-Technische Bundesanstalt (PTB) [Federal Physics and Technological Facility] in Braunschweig to “depict and disseminate the legal time”. Four highly accurate cesium clocks at the facility in Braunschweig keep time 100,000 times more accurately than the Earth does. According to law, the time kept by these clocks is transmitted from a long-wave transmitter DCF 77 in Mainflingen, near Frankfurt am Main. Anyone within 1,500 kilometers who has an appropriate receiver (a so-called “radio timepiece”) can use this time signal free of charge. The exact time, including the correct date, day of the week and month, are transmitted directly to the wrists of people who wear radio wristwatches. In the event of a temporary loss of transmitting capability, or if the recipient is outside the range of the signal, an ordinary quartz movement in the radio watch or clock can continue to accurately keep the time. As soon as the next radio signal is received, the displays on the radio timepiece are automatically synchronized with the norm time as transmitted from the cesium clocks in Braunschweig.

Running Time ( Running Autonomy)

The entire running time of a mechanical movement, i.e. the interval between complete winding of the mainspring and stoppage of the hands due to insufficient energy in the slackened mainspring.

Reference

Specific to each manufacturer, the reference is an alphanumeric sequence used to classify that manufacturer’s watch models. The reference number often contains information about the type of watch, case material, movement, dial, hands, wristband, and presence or absence of precious stones.

Regulator Dial

Off-center indication of the hours and seconds. A seconds hand whose axis is not in the center of the dial makes it possible to read the seconds almost entirely without interference from other hands which seldom eclipse it. Dials of this sort were developed for the so-called “regulators” (precision clocks) that were used to keep time in observatories and watch factories, where timekeeping with to-the-second accuracy was often essential. The Swiss watch industry debuted the first wristwatches with regulator dials in the 1930s. Only a few models were launched, none of which achieved widespread popularity.

Regulating Organ

The regulating organ of a mechanical watch is the balance with its balance spring.

Regulation (Timing, Adjustment)

The timing of a watch movement consists of observing its daily rate in various positions and at various temperatures, then (if necessary) making fine adjustments to optimize the rate. The amount of labor invested in this task is directly proportional to the watch’s quality and its desired degree of precision, which, in turn, is directly proportional to its price. A precision timing according to the official procedure requires the regulation of the movement in at least five positions and at three different temperatures (23.8 and 38 degrees Celsius).

Repair Mark

After a watch has been repaired or refurbished, and sometimes also before a watch is sold, some watchmakers punch a repair mark (usually into the back of the watch’s case). This mark indicates when the servicing was performed and protects a watchmaker against unjustified complaints. Connoisseurs can determine the age and certain other facts about the watch’s “career” by reading the number, type, and (if present) date on the repair mark.

Repassage (Finishing)

Thorough (final) control of a completed watch before it leaves its place of manufacture. Finishing also includes checking the watch’s rate. In the past, repasseurs (finishers) were the aristocrats among watchmakers.

Repeater Strike Train

An elaborate additional function which enables a watch’s movement to audibly announce the current time with greater or lesser precision. Depending on the details of the strike train, one can distinguish among watches with quarter-hour, eighth-of-an-hour (7½ minutes), five-minute, or minute repetition. The strike train needs energy in order to audibly announce the time. It receives this energy when the strike train mechanism is activated. This mechanism is triggered by shifting the position of a slide or depressing a push-piece in the case’s rim. If the slide or push-piece is not shifted all the way to its limiting position, simple repeater watches do not completely ring the time. In finer constructions, an “all-or-nothing” safety device prevents this problem. Watches with this safety device either ring the time either correctly and completely, or do not produce any audible signal at all.

Retrograde Display

A hand which indicates the time, date, or day of the week by incrementally progressing along a calibrated arc and then, when it reaches the end of its arc, quickly jumping back to its original position.

Rhodium Plating

Galvanic ennoblement applied, for example, to the surfaces of the movement. Rhodium plating can protect against tarnishing and give a bright gleam to surfaces. Furthermore, rhodium creates a harder surface. Rhodium can be refined from platinum ore, so it numbers among the metals in the platinum group.

Rotor

An oscillating weight which is free to rotate through a full 360° circle and used on watches with automatic winding. Depending on its design, a rotor mechanism may wind the mainspring in either one or both of the rotor’s directions of rotation. One can distinguish between central rotors and micro-rotors. The former rotate over the entire movement; the latter are integrated into the plane of the movement.

Ruby

The gear train of a timepiece was first equipped with drilled rubies to minimize friction and wear by Fatio de Duillier and French watchmakers Pierre and Thomas Debaufre around 1700. The latter two watchmakers began manufacturing drilled and non-drilled jewels for watch movements in 1704. The first synthetic rubies were used in movements in 1902. The so-called “rubis scientifique” is hard and homogeneous, can be synthesized in whatever color one desires, and is relatively easy to process. It replaced the so-called “reconstituted ruby”, which is made by melting and pressing together fragments of waste ruby. Synthetic rubies differ from natural ones only in their genesis. The chemical composition of each is identical with that of the other.

Rapid Oscillator

Watch movements whose balances oscillate with a vibration number or frequency that has been accelerated to 28,000 or even 36,000 beats per hour in order to minimize their susceptibility to disturbances.

Setting

Circular piece of metal stamped with a hole to accommodate a jewel. To affix the setting to its bar (bridge), it is either pressed or screwed into the bar. The original purpose of the setting was primarily an aesthetic one. Crafted from gold or a metal similar to gold, settings were used to enhance the shine and effect of beautiful jewels. Only later did watchmakers discover the pragmatic usefulness of settings. The jewel inside a factory-made setting can be readily replaced if the stone should break. In the wake of the automated manufacture of watch movements, settings became increasingly more common. Stamps could very precisely punch holes into the bridge to accept the settings. Settings become unnecessary after jewel manufacturers became capable of delivering their products in thoroughly impeccable quality and exactly identical size. These jewels could be pressed directly into holes drilled in bridges, cocks, and plates. Screwed settings are used today because of their attractive appearance. They are most often found in movements made by watch manufacturers in Glashütte.

Stainless Steel

This popular alloy is a combination of steel, nickel, and chrome, with the admixture of molybdenum or tungsten. Stainless steel does not rust, is extremely resistant and nonmagnetic, but is comparatively difficult to process. Wristwatches with stainless steel cases have been becoming increasingly popular in recent years. This is also true for luxury wristwatches with stainless steel cases.

Spring

Springs of various sorts are used in watch movements. In addition to the balance spring and the mainspring, other common types of springs include jumper springs and friction springs.

Spring Bar

A slender cylinder used to affix a “closed” wristband to the horns. The conical pivot on each end of the spring bar is pressed outwards by a cylindrical spring inside the spring bar. To affix a wristband to a watch’s case, a spring bar is first inserted through each end of the wristband, then the sprung ends of each spring bar are pressed inwards and the spring bar is inserted between the “horns” on the case. When the pressure is released, the sprung ends click into place inside the holes which have been drilled into the horns to accommodate them.

Shaped Movement

A watch movement which is not circular. A diverse array of variously shaped movements (e.g. tonneau shaped, baguette shaped, rectangular) have been developed, especially for use in wristwatches. Shaped movements have become quite rare nowadays.

Small Seconds

A seconds hand whose axis is not in the center of the dial. Most small seconds subdials are located above the “6” on so-called “hunter” or “savonnette” watches, in which a 90° angle is formed by the crown, the center of the watch, and the axis of the seconds hand. Some movements are constructed in the so-called “Lépine” style: in these, the crown, the center of the dial, and the axis of the small seconds hand (at the “9”) all lie along the same line. Open pocket watches (i.e. Lépines with their crown at the “12”) have the small seconds at the “6”.

Slideway

Governing device for a chronograph. A moveable cam, the shape of which varies depending on the particularities of the caliber, provides the “programmed” information for the chronograph’s start, stop, and return-to-zero functions. Chronographs with slideway or cam governing are technically less complex, but no less reliable than chronographs with column wheels.

Short-time Measuring Device

A timepiece which measures and supports the immediate reading of the duration of brief intervals. By definition, such devices include stopwatches and chronographs.

Sapphire Crystal

Scratch-resistant material, having a hardness of 9 on the Mohs’ scale, used for watch glasses. Only diamond is harder than sapphire.

Satin Finish

A fine, silky, matte polish given to metal surfaces.

Striking Work, Striking Mechanism

An additional function in a watch which enables the timepiece to audibly announce the time with greater or lesser precision. One should distinguish between timepieces that always automatically ring out the time and those which repeat (ring) only when triggered to do so by depressing a button or shifting the position of a slide.

Swiss Lever Escapement

An escapement for small timepieces in which the teeth of the escape wheel widen with increasing distance from the center of the wheel. The widened teeth distribute the lift given to the escape wheel and the pallets with its two (ruby) pallet jewels. In addition to the Swiss lever escapement, English and Glashütte lever escapements also exist.

Second

The duration of one “secunda diminutiva pars”, i.e. a “second diminished part” of an hour, has been redefined many times in the course of history. These redefinitions were due in part to the tremendous progress made in the science of time measurement. A committee composed of French scientists suggested in 1820 that a second should be defined as one 86,400th of a mean solar day. The empirically determined irregularity of the Earth’s rotation, along with advances in modern quartz timekeeping technology, rendered this definition obsolete. A new definition was proposed in 1956, when the time unit known as the “second” was redefined as one 31,556,925.9747th of the time which the Earth requires to complete one annual orbit of the sun. Noon of January 1, 1900 was chosen as the moment in time to begin counting these annual orbits. This painstakingly defined unit, however, did not survive very long because it was too imprecise. A deviation of five seconds would have accrued within the span of just a single millennium. Quartz timekeepers ceased to play a role in the hairsplitting world of highly precise time measurement because they were replaced by atomic clocks end of the 1950s, so scientists set themselves the task of finding a new definition. Since 1957, the second has been defined as the length of time required by the electron hull of a cesium atom to complete 9,192,631,770 vibrations.

Seconds Display

First introduced by Jost Bürgi in 1579, seconds were originally displayed only on very precise timepieces. Nowadays a seconds hand practically goes without saying on watches and clocks of all sorts.

Self-winding

A synonym for automatic winding in mechanical watches.

Skeleton Movement

A watch movement whose plate, bridges, cocks, barrel and sometimes also rotor are pierced so that the only material which remains is that which is absolutely indispensable to the function of the skeletoned component. Elaborate piercing makes it possible for one’s gaze to penetrate deep into (and sometimes through) the movement. Skeleton work is manually executed and requires a highly skilled watchmaker. The quality of the craftsmanship is most easily recognizable in skeleton work at the junctures where faceted edges meet. Three different kinds of corners can be differentiated: 1. The inset corner. Two facets meet to form an inset corner. The junction should be a perfectly straight line connecting the points of intersection of the two edge lines. This type of corner, which can only be created by hand, proves that the skeleton work is of the very highest quality. 2. The protruding corner. The juncture of two facets forms a protruding corner. This corner should have a sharp edge and should be neither blunt nor rounded. 3. The rounded corner. Unlike the two preceding forms, the facet here does not have a sharp edge. Rounded corners are less artful and less valuable than the other two types of corners because machines can also be used to create them. Wristwatches with skeleton movements debuted in the mid 1930s.

Spiral

Having the form of a spiral. See also: balance spring.

Split-seconds Cronograph

See chronograph rattrapante.

Stop-seconds

A device which halts the progress of the movement and/or seconds hand so that the hands can be set with to-the-second accuracy. To accomplish this, the user pulls the crown outwards the instant the seconds hand reaches the “12”. When he or she hears a time signal, the crown is pushed inwards and the seconds hand (along with the watch’s other hands) resumes its motion.

Stopwatches

Unlike chronographs, stopwatches do not display the ordinary time of day. In simply constructed stopwatches, pressure on a push-piece halts the progress of the movement, thereby also halting the progress of the seconds hand.

Shock Absorption

System to protect the fine and therefore very delicate pivots of the balance staff against breakage. To accomplish this, the bearing jewels and endstones in the balance staff’s bearing are elastically affixed to the plate and balance cock. When the watch is struck by a hard blow, these jewels give laterally and/or axially. A watch with shock absorption should be able to survive unscathed a fall from one meter’s height onto a wooden floor. After the plunge, the watch’s rate should not exhibit any major deviations. Watches with shock absorption systems were first marketed in the 1930s. Shock absorption had become standard equipment by the 1950s. Originally, many watch brands utilized their own shock absorption systems (partly to reduce costs), but these systems did not survive in the long run. The best-known and most widely disseminated shock absorption systems are the so-called “Kif and Incabloc” systems. The latter can be recognized by its steadying spring, which is shaped like a lyre.

Swiss Made

Phrase, printed on the dial and/or stamped into the movement, to identity the provenance of a “Swiss wristwatch”. According to the “Swiss-made ordinance” of May 27, 1992, this phrase may only be used when the movement is Swiss and the assembly, encasing, and final quality-control checks have all been performed in Switzerland. If a watch is to earn the right to bear the phrase “Swiss made” on its dial or movement, then at least 50% of the value of its components, not including the assembly costs, must derive from components which were made in Switzerland. Non-Swiss manufacturers may not use the phrase “Swiss made”, even if all of the components were made in Switzerland, but the assembly was performed outside of Switzerland.

Swiss Mvt. (Movement)

A phrase printed in small letters on the dial of non-Swiss wristwatches that encase a movement which was made in Switzerland. The phrase “Swiss Mvt.” is found, for example, on plagiarized copies. Usually printed in miniscule letters, the phrase may mislead an unwary purchaser to misread and mistakenly assume that the second word in the phrase is “made”.

Three-quaters Plate

Unlike bridge-type movements, nearly the entire gear train (with the exception of the pallets, escape wheel, and balance) is borne beneath an additional plate. Three-quarters plates are used in American and English watches, and above all in watches made in Glashütte.

Tuning Fork Watch

An electronically excited tuning fork, oscillating at a frequency of 360 Hz, serves as the regulating organ. The best-known tuning fork watch is Bulova’s “Accutron”, which debuted in 1960.

Tachometer Scale

A scale, printed on the dial of a chronograph, to assist in the calculation of average speeds. Tachometer scales are typically calculated for one kilometer or one mile. The chronograph is switched on at the starting point of a measured stretch, e.g. the instant one’s car passes a kilometer post along the roadside, then switched off again when one’s vehicle reaches the end of the measured kilometer. The chronograph’s seconds hand now points to the numerals on the tachometer which correspond to the average speed (in kph or mph) at which the measured stretch was traversed.

Telemeter Scale

A scale on a chronograph to enable the wearer to directly read distances. The basis for the calculation is the difference between the speeds with which sound waves and light waves propagate in air. For example, the distance between the wearer and a storm can be determined as follows: the chronograph is switched on the instant a flash of lighting is seen, then stopped when the corresponding thunderclap is heard. Depending on whether the telemeter scale is calibrated in kilometers or miles, the chronograph’s seconds hand will point to the numeral on the telemeter scale which corresponds to the storm’s distance (in kilometers or miles) from the observer.

Tourbillon

Invented by Abraham-Louis Breguet in 1795 and patented by its inventor in 1801, the tourbillon is a device which compensates for the center-of-gravity error that afflicts the oscillating system (balance and balance spring) of a mechanical watch. The French word “tourbillon” means “whirlwind”. The device is appropriately named because it encloses the entire oscillating and escapement system within a rotating cage of the lowest possible weight. This cage completes one rotation around its own axis during a particular unit of time (usually one minute). Thanks to its ceaseless rotation, a tourbillon compensates for the negative influences that the Earth’s gravitational attraction exerts on the balance when the watch is held in a vertical position, thus leading to corresponding improvements in the precision of the rate. The tourbillon has no effect on the precision of the rate when the watch is held in a horizontal position. Wristwatches with tourbillon mechanisms were first crafted as contestants in chronometer competitions in the 1940s. Wristwatches with tourbillons have been manufactured in small series since 1986.

Twenty-four-hour Display

A wristwatch has a 24-hour display if its hour hand completes one full rotation around its own axis in the course of a full day and its dial is calibrated from 1 to 24. This type of display is rarely seen because it takes some time to become accustomed to it and is difficult to read. Some wristwatches also have two separate hour hands: one of the two rotates around its own axis once every 12 hours; the other hour hand completes the same orbit in 24 hours.

Vibration Number

The sum of the beats of the rate-regulating organ (e.g. pendulum or balance) of a timepiece is described as its “vibration number”. One full oscillation consists of two sequential vibrations. For example, classical wristwatches generally have an oscillating frequency of 18,000 vibrations (or “beats”) per hour. In other words, the balance completes 9,000 oscillations (beats) or 18,000 half-oscillations (vibrations) per hour. The frequency of the balance of such a watch is 2.5 hertz (Hz).

Water-resistant Wristwatches

The commonly seen phrase “water-resistant to 30 meters” (3 bar or 3 atmospheres) is based on German industrial norm (DIN) no. 8310. According to this norm, a watch is entitled to bear this phrase on its dial if its case is resistant to perspiration, sprayed water, and rain, and is impermeable to water for at least 30 minutes when submerged to a depth of one meter. The additional items of information “30 m”, “3 bar” or “3 atm” are not subject to regulation, but nonetheless indicate that the watches which display this information have passed corresponding pressure tests to which their manufacturers have subjected them. Nonetheless, it is not recommended that such watches be worn while swimming, and surely not while scuba diving.

World Time Indication

Beginning at zero degrees longitude (i.e. the Greenwich meridian), the time differs by one full hour with every 15 degrees of longitude. The world’s system of time zones was first introduced by Canada and the USA in 1883. Germany began to comply with this system in 1893. Watches with world time indication may show as many as 24 time zones on a single dial. An additional mechanism supports the simultaneous display of the time in more than one time zone. (A so-called “heure universelle” may display the time in as many as 24 different zones.) Watches with world time display have been available since the 1930s and are particularly useful for people who fly on long-haul flights or for businesspeople who frequently have telephone conversations with business associates in distant places. In the wake of the renaissance of the mechanical wristwatch, a wide variety of different world time systems have been developed.

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