The Language of Haute Horlogerie

Time display with a dial and hands.

Watches are protected against magnetic influences mainly by antimagnetic components. IWC's Ingenieur model, for example, was resistant to magnetic fields of up to 500,000 A/m.

Term for the parts of the escapement. A steel assortment consists of a pallet fork and an escape wheel made of steel.

With automatic winding, the mainspring is tensioned by an oscillating weight driven by the movement of the wrist.

Rectangular, particularly narrow movement for ladies' jewellery watches, with a compact gear train arranged on two levels.

Coiled spring attached at its inner end to the balance staff and at its outer end to the balance cock. Originally made of steel, later of Elinvar, today of Nivarox. Together with the balance wheel it generates the frequency.

Also known as the balance or regulating organ: a time-giving flywheel that enables the hands to advance evenly. The balance spring returns it again and again to its position of rest. It is held in ruby bearings — the staff is approximately 0.10 mm thick.

In older wristwatches, banking pins prevent the pallet fork from swinging too far. In more recent watches, they have been replaced by milled recesses in the mainplate.

Metal used in the manufacture of the Glucydur balance wheel.

Ring fitted to the middle part of the case that holds the crystal. As a rotating bezel with a marker and scale, it serves, for example, to measure a period of time or to read additional time zones (see GMT). Diving watches according to ISO 6425 require a secured display of the dive time, e.g. a unidirectional rotating bezel; other bezels carry scales such as the tachymeter.

Formerly compensated for temperature fluctuations that adversely affect the rate of the watch.

A special balance spring with a raised terminal curve — for a long time a hallmark of precision watches.

Part of the movement blank that holds the bearings of the wheels, secured with two screws. There are winding bridges and gear-train bridges. See also Cock.

The rear plate of the movement, consisting of several bridges and cocks.

Decorative stone polished into a rounded shape, often set in the winding crown.

Abbreviation of “calibre” — French for movement or calibre. Usually accompanied by the manufacturer’s designation and a number (e.g. ETA 2892-2), often with a size specification (e.g. 13''). The designation “R” stands for “rectangulaire” (rectangular).

See cal.

In wristwatch chronographs, the simpler construction without a column wheel — controlled via a switching lever. Only came into use after the Second World War.

Further reduces the friction of the bearing and limits the axial play (end shake). Always used in the balance bearing, occasionally also in the escape wheel bearing.

Brass or steel plate holding the cap jewel, secured with one or two screws.

The seconds hand is driven from the centre of the dial — like the hour and minute hands. Initially found in inexpensive watches, from the mid-1930s also in high-quality wristwatches. With off-centre (small) seconds, the display is shown on a small subsidiary dial.

Usually the centrally positioned wheel carrying the minute hand. Via its pinion it receives the power from the barrel and transmits it to the third wheel.

In high-quality wristwatches, ruby jewel bearings set in gold, sometimes fixed to the mainplate with two or three screws (screwed chatons).

Wristwatch with an additional mechanism for timing intervals — up to 30 or 45 minutes, and in more complex models up to twelve hours. The chronograph hand is centrally mounted; sub-dials are used for recording minutes and hours. A distinction is made between designs with a column wheel and those with cam switching.

High-quality watch regulated in various positions and at different temperatures. Its rate accuracy is tested by an official institute and confirmed with a certificate.

Escapement developed by the Englishman George Daniels (1926–2011) and produced industrially by Omega since 1999. The balance wheel receives its impulse directly in one direction of oscillation and via the pallet fork in the other. Smaller contact surfaces result in less friction, and the escapement requires less lubrication.

Part of the ébauche that supports a wheel or the balance wheel — held by only one screw and one locating pin. See also Bridge.

In chronographs, the higher-quality of two designs. Made of steel, with seven to nine sturdy pillar-shaped teeth. Controls the start and stop functions and prevents unintentional resetting to zero.

Additional mechanism that can only be made by specialists. These include the repeater, the perpetual calendar and the chronograph.

Abbreviation for Contrôle Officiel Suisse des Chronomètres, the official Swiss chronometer testing institute founded in 1973. It tests the rate accuracy of movements and, if they pass, awards the designation chronometer. Mechanical movements are tested according to the ISO 3159 standard over 15 days in five positions and at 8, 23 and 38 °C; their mean daily rate must lie between −4 and +6 seconds.

See Hand-wound.

The smaller gear wheel on the barrel bridge and part of the crown winding mechanism. It meshes with the ratchet wheel and connects the winding stem to the mainspring. Made of steel.

The date display was originally indicated by a central hand and a ring of numerals around the outer edge of the dial. Today it is predominantly shown digitally in a window, usually at the “3” hour marker.

Time display using numerals instead of hands — in an aperture or on a screen.

French for movement blank. Today it refers to the gear train with winding mechanism — without escapement, balance wheel and mainspring.

A form of fine regulation: the index on the balance cock forms a fork with a screw at its end. Turning this screw allows micrometric regulation of the rate.

Wristwatch with an oversized barrel. The driving force of the mainspring lasts for at least one week. A rare movement.

Consists of the pallet fork and escape wheel. Located between the gear train and the regulating organ, the balance wheel. Prevents the movement from running down uncontrolled and lets the gear train advance step by step in time with the balance.

Manufactures such as Patek Philippe or IWC keep ledgers containing all relevant data on the watches they have delivered. For a processing fee, an extract from the archives is issued for each watch.

Compensates for variations in the watch's rate. Watches are finely adjusted by specialists in various positions and at various temperatures — usually with a fine regulator for shifting the regulator index in micrometre increments.

Additional function of a chronograph, in French "retour en vol": a single press of the reset pusher stops the running chronograph hand, returns it to zero and restarts it immediately. The three operating steps otherwise required are eliminated. The function is used above all in air navigation to measure successive time intervals.

Refers to the one-sided mounting of a wheel, without a second, opposing bearing. Used in particularly thin constructions.

The oscillation rate of the balance wheel, nowadays given in hertz (1 Hz = 1 oscillation per second). Common frequencies in mechanical wristwatches: 2.5 Hz · 2.75 Hz · 3 Hz · 4 Hz · 5 Hz — corresponding to 18,000 to 36,000 vibrations (semi-oscillations) per hour.

Displays the day of the week and the month. Due to the varying lengths of the months, the days of the week must be corrected manually. Many models are equipped with a moon-phase display. See also Perpetual calendar.

Takes the energy from the barrel and transmits it via pinions and gear wheels to the escape wheel. In wristwatches: centre wheel, third wheel and fourth (seconds) wheel.

Quality seal for particularly high-grade products by Geneva manufacturers. It shows the coat of arms of the Swiss city and always stands for chronometer quality. A similar hallmark of quality exists in Besançon.

Abbreviation for Greenwich Mean Time — the mean solar time at the prime meridian in Greenwich, London. The reference point for dividing the Earth into 24 time zones. A classic example of this complication: the “GMT” by Rolex.

Decoration of fine, repeating straight or curved lines that intersect or overlap and create a play of light. It is engraved with a graver or a guilloché machine; when the guillocheur operates the machine by hand, it is called hand guilloché — as distinct from industrial processes such as stamping or CNC machining. In watchmaking it has been applied to dials since the 1650s and to cases since 1770.

Winding via the crown mounted on the side of the case. In the rocking-bar winding system of simple watches, switching to hand-setting is done by a rocking bar; in the technically more elaborate clutch (sliding-pinion) winding system, this function is performed by the clutch wheel.

Valve in the case of diving watches for saturation diving. In this type of diving, divers breathe an oxygen-helium mixture; the very small helium atoms can penetrate the case through the gaskets under pressure. The valve lets them escape during decompression so that the excess pressure inside does not blow off the crystal. See also water resistance.

Found on early wristwatches, occasionally up to the late 1930s. Until the mid-1920s, hingeless cases often had an alignment pin for positioning when closing.

When the balance wheel oscillates isochronously, the period of oscillation is independent of the amplitude — the oscillations take equal time. Long a central theme of the watchmaking art.

Term for the moving figures on the dial of a repeater watch.

Made of rubies — today predominantly produced synthetically. They reduce wear on the arbor ends (pivots) and lessen friction. Today pressed into the mainplate without a setting, with a recess to hold the lubricant (oil sink).

English term for the number of jewels in the movement — e.g. “SEVENTEEN (17) JEWELS”. See Jewel bearings.

A detached escapement found in all high-quality wristwatches.

Unit of length in watchmaking. 1 ligne (1'') = 2.256 mm. Common sizes for wristwatch calibres range between 5 ½'' and 13''.

Complicated wristwatches produced in very small series or for special occasions — usually numbered consecutively on the dial or caseback (e.g. 150/500).

The base plate on which the movement is built. In wristwatches, the second plate usually consists of bridges and cocks.

Stores the energy needed to run the watch and drives the gear train. In more recent watches it is unbreakable and rustproof (see Nivaflex).

In the narrower sense, a watchmaker that designs, develops and produces all or almost all components of the watch itself, starting from the raw movement (ébauche) — as distinct from the établisseur, which assembles bought-in parts. There is no uniform definition; in the broader sense, the term refers to makers that largely develop and produce their movements themselves.

Robust wristwatches, from 1912 onwards with radium-luminous hands and numerals, many with a protective grille over the crystal and a black contrasting dial. Later models were in some cases given a 24-hour display — for example for American paratroopers.

Complication that chimes the time audibly on demand — activated by a slide or pusher: one hammer strikes the hours on a low-pitched gong, two hammers strike the quarter-hours as high-low double strikes, and finally the minutes elapsed since the last quarter-hour sound on the high-pitched gong. At 12:59 this means 12 low strikes, three double strikes and 14 high strikes.

A popular complication: the moon travels through a window aperture depicting the night sky and shows the changing phases of the moon during the lunation, which lasts 29.5 days on average.

Serves to display the time: cannon pinion with toothed rim, minute wheel (intermediate wheel), hour wheel and setting wheel. The rotation of the centre wheel is transmitted to the hour wheel at a ratio of 12:1.

Fatigue-free, unbreakable mainspring made from a special alloy of beryllium, molybdenum, nickel, cobalt, iron, tungsten and titanium. With an extremely favourable power-delivery curve. Replaced the steel spring after 1950.

Hairspring made from the Nivarox alloy (iron, nickel, chromium, titanium, beryllium). Rustproof, non-magnetic, as elastic and hard as steel — and insensitive to temperature fluctuations. Replaced the more expensive compensation balance.

Also known as a B-Uhr: a large wrist chronometer with a stoppable central seconds hand for setting the time precisely. Used by the German and Swiss air forces during the Second World War.

The pallet fork receives the impulse from the escape wheel and transmits it to the balance wheel. In the Swiss lever escapement, the pivot points of the escape wheel, pallet fork and balance lie in a straight line. If this is not the case, it is referred to as a lateral pallet fork.

Parts of the jewelled lever (pallet fork), fitted with two synthetic rubies. They are ground at an oblique angle so that the escape wheel teeth can slide along them. In small watches they are always made of ruby — and are included in the jewel count.

Highly complex mechanism that advances the entire calendar automatically — from the varying lengths of the months through weekday and month to leap years. Usually combined with a moon-phase display. Produced only in very small numbers. See also full calendar watch.

Simplified lever escapement without jewelled pallets — found in simpler watches.

A toothed wheel for transmitting power with more than six but fewer than 20 teeth (leaves).

The ends of a wheel or pinion arbor, which run in rubies or in bearings without jewels. See also Jewel bearings.

Slight deviations in the rate of a wristwatch in different positions — resulting from bearing friction, imbalance of the balance wheel and the centre of gravity of the balance spring.

An appealing additional indication that makes the state of the power reserve visible. It became popular with the introduction of self-winding, but remains relatively rare to this day.

Allows the date to be set quickly via the crown — without having to turn the hands forward through 24 hours.

Part of the crown-winding mechanism and of the click work (ratchet wheel, click, click spring). Sits on the barrel bridge; made of steel.

See split-seconds chronograph.

Optimisation of the rate by altering the effective length of the balance spring by means of the regulator. Good watches are adjusted in two positions ("2 ADJUSTMENTS"). See also fine regulation.

Located on the balance cock and adjustable. It is used to regulate the rate of the watch. Formerly fitted with a pointer extension to make its position on the plus-minus scale easier to see.

Models from the 1920s and 1930s are often reissued — usually with modern self-winding movements and not as exact copies. Originals differ, among other things, in the absence of shock protection for the balance wheel.

The dial indications are not arranged in a circle. At the end of the scale, the hand jumps back to its starting position.

Electroplated metal coating of rhodium (a platinum-group metal) — used as surface protection and to embellish high-quality movements. Gives a shiny, silver-coloured appearance.

Oscillating weight of the automatic winding: a freely rotating metal segment, usually made of a high-density material (e.g. tungsten-based), which winds the mainspring via a gear train when the arm moves. Depending on the design, it winds in both directions of rotation or in one only. A small, off-centre micro-rotor recessed into the movement enables particularly thin automatic movements.

Watch crystal made of colourless, synthetically produced corundum (aluminium oxide). Sapphire has a Mohs hardness of 9, making it highly scratch-resistant, and is used above all in high-quality watches. Sapphire crystal reflects light almost twice as strongly as mineral glass; anti-reflective coatings on one or both sides compensate for this.

In mechanical wristwatches the seconds hand makes five steps per second; in quartz watches only one. The hacking seconds (stop-seconds) function brings the hand and the balance wheel to a standstill for setting to the exact second. The “flashing” seconds (“seconde foudroyante”) rotates once around its axis in four or five jumps per second. See also Centre seconds.

Transmits the power to the pinion of the escape wheel.

Movements whose outline departs from the circular — oval, rectangular or shaped. An expression of the independent development of the wristwatch. The stated dimension refers to the width of the calibre.

Primarily protects the delicate pivots of the balance staff. The most proven solutions are elastic jewel bearings such as the Incabloc system.

Balance spring made of monocrystalline silicon, produced from silicon wafers by deep reactive-ion etching (DRIE). Silicon is antimagnetic, corrosion-resistant, shock-resistant and light; oxidation also allows the spring to be compensated against temperature fluctuations. In watchmaking, silicon has been used since the 2000s mainly for parts of the regulating organ.

Mechanical watch, usually hand-wound, whose mainplate, bridges and other movement parts, as well as dial and case, are openworked and heavily thinned or made of transparent material. This makes the balance wheel and spring, winding and hand-setting mechanisms visible.

Also known as a Rattrapante: a chronograph with two superimposed hands for measuring intermediate times. The split-seconds hand can be stopped via a pusher and then brought back into alignment with the main hand.

Connects the watch and the strap. Spring-loaded and seated in the holes of the lugs. In use since the 1930s.

Trade name of a non-radioactive luminescent pigment based on strontium aluminate, manufactured under licence by the Swiss company RC Tritec AG. It derives from LumiNova, invented in 1993 by Nemoto & Co. in Japan, which replaced radium- and tritium-based luminous compounds (see military watches). Once charged by sunlight or UV light, it glows in the dark and fades after a few hours.

Special regulator for fine adjustment of a watch. A swan-neck-shaped spring applies pressure to the regulator index, while a fine screw secures its position.

Scale on the dial or bezel which, together with the chronograph, allows an average speed to be determined. The time taken over a known distance, e.g. 1,000 metres, is measured; the chronograph hand then indicates the speed directly on the scale. 45 seconds for 1,000 metres corresponds to 80 km/h.

Device in which the escapement and balance wheel together with the balance spring sit in a rotating carriage (cage) that usually turns once a minute about its own axis. This evens out the gravity-induced rate deviations in the vertical positions (see positional error). Abraham-Louis Breguet received the patent on 26 June 1801.

Holes without jewels in the movement in which the arbor ends of wheels or pinions run. Found mainly in inexpensive watches.

Ability of the case to prevent water from entering; gaskets are fitted at the crystal, caseback, crown and pushers. According to ISO 22810, a watch may be called "water-resistant" if it withstands an overpressure of at least 2 bar; higher ratings in bar (or converted into metres) state the tested overpressure. Such watches are not designed for scuba diving — diving watches are governed by ISO 6425 (at least 100 m).

A wristwatch with a scale disc showing the 24 time zones, each marked by a city name. See also GMT.