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Annual calendar (watch)

A full or partial simple calendar that takes automatically into account months with less than 31 days or leap years, but not of leap years. It must be adjusted once a year.

Arabic numerals

1, 2, 3, etc.
Arabic numerals, which were widely used on watch dials towards the eighteenth century, allow greater scope for fantasy than their Roman counterparts.
The majority of fine-quality watch companies use both Arabic and Roman numerals without distinction.


The positioning of the different parts of the movement or of the watch in relation to each other.

Atm (atmosphere)

Unit of measure to indicate a watch's water-resistance, specifically its capacity to resist pressure, based on standard atmospheric pressure defined as 1013 hectopascals or approximately 1 bar.
Can be expressed in different ways: 10 atm = 10 bar = 100 metres water depth.

Automatic (Self-winding)

Describes a mechanism that winds the mainspring by using the movement of the arm to cause a rotor to rotate and which, via specific gears, winds the mainspring.


In a watch case, the cover, transparent or not, opposite the dial.


A circular, moving part which oscillates on its rotational axis. It is coupled to the balance-spring which gives it the to-and-fro motion through which it divides time into strictly equal parts. Each to-and-fro movement ("tick-tock") is called an oscillation, and each oscillation comprises two vibrations.
A circular mass (rim) held by spokes. Combined with the spiral it forms the regulating organ of the watch.


A device that produces electrical energy through a chemical reaction. Typically, a battery lasts for two to five years. Its lifespan depends on the type of watch, and the amount of energy required for the different functions. For example, a working chronograph will consume more energy than a watch that shows only hours, minutes and seconds. Watch batteries are either silver-oxide or lithium.

Some lithium batteries have a theoretical lifespan of 10 years.


A ring around the case middle that secures the crystal.
A rotating bezel records additional information such as the duration of a given phenomenon.
The bezel on a diving watch is unidirectional. This is a deliberate feature and an additional safety factor as the bezel only rotates in the direction that will reduce dive time. Hence if the bezel is accidentally turned, the diver can still surface with sufficient air and respect decompression stops.


Synonym of size. Sully used this term circa 1715 to denote the layout and dimensions of the different movement pillars, wheels, barrel, etc. Since then "calibre" has been used to indicate the shape of the movement, its bridges, the origin of the watch, its maker's name, etc.
Now designates the movement itself.
The round calibre is the most commonly encountered. It is described in terms of its casing diameter, measured in lignes or millimetres, for example a 10''' / 22.5 mm round calibre. The shape and layout of the bridges is used to distinguish between a bridge calibre, in which each part of the train has a bridge, the revolver calibre, whose barrel bridge bears a slight resemblance to a pistol, the curved bridge calibre, where the bridges curve towards the centre of the movement, and the three-quarter-plate calibre in which the entire train except for the escape-wheel is fitted under a bridge that covers some three-quarters of the movement.


Container that protects the watch movement from dust, damp and knocks.
The case is part of the watch's appearance and, influenced by fashions and buyers' personal taste, must have visual appeal.
The main parts of a Lépine pocket watch case are the middle, inside which the movement is secured, and the caseband. On the bridge side, the middle of the case is closed by the back cover (sometimes with a second cover inside called a cuvette). On the dial side it is closed by the bezel that secures the glass.


A watch indicating hours, minutes and seconds combined with a mechanism whose hand can be started, stopped and returned to zero on demand to measure a duration to one fifth, tenth or even hundredth of a second. Subcounters for the minutes and hours (usually 30 minutes and 12 hours) totalise the number of revolutions by the chronograph hand. The accuracy of these recorded times can only be guaranteed if the chronograph has satisfied the criteria of the "chronometer" label.
The first chronographs deposited drops of ink on their dial; this no longer being the case, strictly speaking a chronograph should be called a chronoscope.

Chronometer (general definition)

A chronometer is, etymologically, an instrument for measuring the time. With usage it has come to mean a high-precision watch displaying seconds whose movement has been controlled over a period of several days, in different positions and at different temperatures, by an official neutral body. Only mechanisms that have satisfied the criteria for precision of ISO 3159, or its equivalent, are issued with an official chronometer certificate.
In Switzerland, the Contrôle Officiel Suisse des Chronomètres (COSC) has the power to award these certificates. Based on the requirements of ISO 3159, the COSC has also drawn up a set of specifications for the testing of quartz movements.
While a chronograph can be used to measure an interval of time, it can only use the name "chronometer" if it has been officially certified as such.


Clarity is the absence of inclusions in a gemstone. The clarity scale for diamonds runs from IF (Internally flawless, with no internal characteristics), to I3 (having many clearly visible inclusions using the naked eye). A ten-power loupe is used to examine a diamond for clarity.


Any function other than the indication of hours, minutes and seconds, regardless of whether the mechanism is hand-wound or self-winding, mechanical or electronic, and of movement height. The tourbillon and the self-winding system are considered to be complications even though they do not fall within the generic definition.
Far from being a passing fad, complications were instrumental in the rediscovery of the watchmaker's art in the 1980s and have continued to play an important role in the development of the traditional wristwatch. Complications fall into two categories according to whether they are or are not related to timekeeping.

Côtes or vagues de Genève

A decoration of undulating lines, like waves, frequently used to embellish superior quality movements.

Crown (watchmaking)

The winding crown is a knurled or fluted button of various shapes, held between the thumb and forefinger and used to wind the watch. Some crowns incorporate a mobile pushbutton for operating a chronograph mechanism or to release the cover of a hunter case.
The first example of a crown for winding and setting the time appeared on a watch made by John Arnold in 1820. The system was perfected by Breguet for miniature watches circa 1832, and was patented in 1838 by Louis Audemars in Le Brassus. In 1844, Adrien Philippe invented and patented his sliding pinion mechanism which would replace all other systems.
In 1847, Charles-Antoine LeCoultre invented his keyless winding system with its rocking bar and side pushbutton to set the time.


A crystal is a mineral whose atoms form a very regular structure. Most gemstones are found as crystals.


A plate of metal or another material which, in a standard clock or watch, serves to indicate hours, minutes and seconds. Dials come in an almost limitless variety of shapes, decorations, materials, etc.

Indications are given by numerals, graduations or markers in different styles.
• An aperture dial has openings (apertures) through which the time indications can be read.
• A thirteen-piece dial comprises 12 enamelled cartouches for the hours set around a thirteenth central enamelled piece, often decorated and with the maker's signature.
• A calendar dial gives calendar indications such as the day, date, month, year and religious festivals.
• A multiple time zone dial (see complication) gives the time in two or more zones.
• A dial with tide gauge (see complication) gives high and low tide times for a given location.
• A regatta dial (see complication) has a countdown function enabling competitors to position themselves as near as possible to the starting line in the minutes leading up to the race.
• An orienteering dial (see complication) features a hand which, driven by a specific wheel and making one complete revolution of the dial in 24 hours, shows North when the hour hand is pointed towards the Sun.
• A diving dial (see complication) indicates surfacing time and possibly also decompression stops and times.


Diamond is the hardest and most luminous precious stone.
The price of a diamond is calculated according to the 4C criteria: Cut - Carat - Clarity - Color.
The weight of a diamond is expressed in carat: 1 carat is equal to 0.20 gram.
Pure colourless carbon, in jewellery the diamond is cut into facets to increase its sparkle.
In watchmaking it is used to decorate straps, cases, bezels, etc.
Today, the fine watchmaking and fine jewellery's brands purchase diamonds in line with the certification requirements of the Kimberley process and the associated guarantee systems set up to put an end to “war diamond” trade.

Dual time zone

Describes a watch that simultaneously gives the time in two time zones, usually local and the wearer's home.


A mechanism that is fitted between the gears and the regulating organ. Its function is to suspend the gears' motion at regular intervals and to supply energy to the balance.

The main types of watch escapement are:
• recoil escapements (verge or crown wheel)
• dead-beat escapements (cylinder, virgule, double virgule)
• detached escapements (lever, detent)

The lever escapement is by far the most common today. Exceptional watches may be fitted with a different kind, often a detent or virgule escapement.
In terms of escapements, one can historically speak of the lever and indeed the Swiss lever type, given that the Swiss lever escapement is the most widely used today because it is especially suited to watches and chronometers.


A procedure for manufacturing the watch and/or movement by assembling the various parts. As a general rule, the procedure in full comprises taking delivery of, inspecting and stocking the ébauches, the regulating parts and other components for the movement and exterior; assembly; timing; fitting the dial and hands; fitting the movement and the final inspection before packaging and dispatching.

Finishing (Finissage)

The final operation in a process.
On a watch case, the last stage in assembling the parts so that they function.

Fly-back (Retour en vol)

A function of particular use to pilots by which the chronograph hand can be reset to zero and immediately started again by pressing once on the pushpiece.
Indeed, the operation of stopping, returning to zero and restarting the hand in three separate movements would be too time-consuming at high speed.

Folding buckle

An articulated buckle that unfolds when opened. Should the buckle accidentally come open, it will still hold the strap sufficiently in place to prevent the watch from slipping off the wrist.


The number of oscillations per second, measured in Hertz (Hz). The balance makes a to-and-fro movement at a given frequency (two vibrations = 1 Hz). The higher the frequency, the more accurate the watch: 21,600 vib/h (3 Hz), 28,800 vib/h (4 Hz) and 36,000 vib/h (5 Hz).

The quartz in an electronic watch vibrates at a high frequency, generally 32,768 Hz (commonly abbreviated to 32 kHz).


Gemological Institute of America.


Gold has seduced the world with its beauty, but also because not even acid can alter its natural properties. An estimated 130,000 tons have been extracted from the earth since prehistoric times, of which 100,000 tons in the twentieth century alone. Gold is a malleable substance (with a hardness of just 2.5) and therefore easy to work with. It can be used in an alloy with other metals, often silver and copper. These alloys increase its resistance and change its color.

An 18k (karat) or 750 gold alloy is generally yellow, pink, red or white. A color standard exists for the first three shades. Each has the same base of 750 parts per thousand of gold; the yellow, pink or red color is obtained by varying the proportion of silver or copper that make up the remaining 250 parts. White gold is an alloy with palladium (previously nickel) and is frequently rhodium-plated to enhance its whiteness. Thanks to the phasing-out of nickel in white gold in the early 1990s, and the advent of white gold solder in the same color as the alloy, large items can be made in white gold without rhodium plating which, being only a thin layer, has the disadvantage of rubbing off locally over time.

Other colors of gold exist but are rarely used:

• Blue gold: an alloy of gold and iron. Heat treatment oxidizes the iron molecules at the surface of the metal, producing the blue color.
• Green gold: an alloy of gold, silver and copper.
• Black gold: obtained by means of chemical vapour deposition (similar to PVD) of atoms of gold, carbon and other metals. The black coating is just a few microns thick. Other surface treatments use electrodeposition of rhodium, chromium and very dark impurities.
• Brown gold: obtained by chemical treatment.


An abbreviated means of referring to a leather watchstrap.


A new-generation luminous substance, used to coat hands and numerals. It stores light which it then emits in the dark causing the hands and numerals to glow and continue to be visible. Previously, radium salts were used which, because of their too dangerous radioactive properties, were replaced by Tritium and more recently by Super-LumiNova, a non-radioactive aloxide.
LumiNova® is a registered trademark of Nemoto and Co. Ltd


Describes a movement that is wound by hand using the winding crown.


The position held by a master.
In Switzerland, a master must take an exam and have several years' experience as a watchmaker-repairer. In Geneva, the first masterships date back to 1601.


A configuration of parts to perform a function.
The watch is a mechanism whose various parts are themselves mechanisms, each with a specific function.
Chronograph mechanism: combination of parts to start, stop and reset the chronograph hand(s).
Repeater mechanism: combination of parts that triggers the striking mechanism and activates the hammers.


Natural mother-of-pearl is the iridescent surface of the inside of certain shells. It is used as watch dials giving big stainless steel watches a rich appearance.
Synthetic mother-of-pearl is made from fish scales and horn.
Mother-of-pearl has opalescent shades.


The assembled organs and mechanisms of a watch, namely the winding and hand-setting mechanism, the mainspring, the gears, the escapement and the regulating organ (balance and spring).


The iridescent substance secreted by molluscs around a foreign object. Pearls and cultured pearls are covered with nacre by certain species of oysters and mussels.

Perpetual calendar

Devised to incorporate the specificities of the Gregorian calendar. It is perpetual because it automatically adjusts to months with 30 days and to the 28 or 29 days in February. For this, it incorporates a mechanical memory whose sequences are repeated every 48 months to correspond to the cycle of leap years. It must only be adjusted for the exceptionnally non-leap year years, the next being 2100 and 2400.


To give a mat or shiny finish to a smooth surface.
For example: mirror polish (black polish).

Power reserve, Indicator

A visual indication of how long a watch will function before the mainspring must be wound.
Power reserve: the duration, given in hours or days, a fully-wound watch will function without being wound again.


A button that commands a function, for example to open a case cover or to start and stop a chronograph.


Quartz, used as a regulating organ, has the specific property of vibrating at a very high frequency (32 kHz) when placed under an electric current (piezoelectric property). Under certain conditions, it imparts its own vibration frequency to the circuit, which divides it into precise units of time. This property has been used in electronic watches since the 1970s.

The quartz used in electronic watches is industrially-manufactured synthetic quartz.

Roman numerals

I, II, III, etc.
Roman numerals have traditionally been used on clock and watch dials.
IV is often given as IIII to create visual symmetry with the VIII. Only the IX is written using the subtractive principle.


A very hard, naturally occurring, red stone that is a variety of corundum (aluminium oxide). Ruby is especially suited to making bearings (jewels) for the watch's different moving parts and for the organs of the escapement, thereby reducing friction to a minimum.
Drilled rubies were used for the first time by Nicolas Fatio de Duillier in 1704. Genuine rubies have now been replaced by synthetic rubies.

As a general rule, a simple mechanical watch, i.e. one that indicates hours, minutes and seconds, should have at least fifteen jewels at the points most exposed to friction.


Sapphire is a variety of corundum that occurs in multiple shades of blue, and in many other hues - mauve, yellow, orange, pink-orange (Padparadscha), green,  black... - except red (red corundum is ruby). Six-sided asterisms sometimes occur in star sapphires, caused by inclusions of tiny, thin, parallel needles of rutile. Many sapphires are heat treated to improve their colour and transparency. Sapphire has a hardness of 9 and a specific gravity of 3.9 - 4.1.

Colourless synthetic sapphire is widely used to make watch crystals.


A fastening comprising a cylindrical shaft, grooved along part or all its length, and a head with a slot for the screwdriver.


The basic unit of time corresponding to 1/86,400 of the mean solar day, which is the period of rotation about its own axis of an ideal Earth describing a circle round the Sun in one year, at a constant speed and in the plane of the Equator.

In the post-Second World War period, atomic clocks reached a degree of precision that could demonstrate the infinitesimal irregularities (a few hundredths of a second per year) of the Earth's rotation about its own axis. It was then decided to redefine the reference standard. This new definition was ratified by the 13th General Conference on Weights and Measures in 1967 as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."

Conventionally, the second is subdivided into tenths, hundredths, thousandths (millisecond), millionths (microsecond), billionths (nanosecond) and trillionths (picosecond).

In a watch, seconds are indicated by the fourth wheel and the seconds hand.

Foudroyante (Jumping seconds or hand) (Flying seconds)

On a chronograph, a hand that makes one rotation every second, pausing four, five, even eight times to indicate quarters, fifths or eighths of a second.
Also called foudroyante.

Secret spring

A spring that releases the cover on a hunter watch case.

Self-winding (Automatic)

Describes a mechanism that winds the mainspring by using the movement of the arm to cause a rotor to rotate and which, via specific gears, winds the mainspring.


A means of attaching the watch around the wrist. A strap can be in gold, silver, steel, leather, etc. and in styles from the simplest to the most elaborate.


An instrument for measuring speed.

In watchmaking, a chronograph or sports counter with a scale for reading speed in kilometres per hour (kph) or another unit.


A system devised and patented by Abraham-Louis Breguet in 1801 to compensate for errors of rate caused by the Earth's gravitational force in upright positions. The escapement is mounted in a revolving cage with the regulating organ (balance) at the centre.

The escape-wheel pinion turns about the fixed fourth wheel. The cage generally revolves once a minute and, in doing so, compensates for errors of rate caused by the vertical position in which pocket watches spend most of their time.

This delicate and complex structure is one of watchmaking's most ingenious mechanisms. A simplified and more robust alternative is the karussel where the cage is driven not by the fourth wheel but by the third wheel. A tourbillon can contain a lever or a detent escapement.


A chronograph or subdial featuring a telemeter scale with which to measure the distance between an event and an observer based on the speed of sound.

Vagues de Genève

Synonym of Côtes de Genève. A decoration of undulating lines, like waves, frequently used to embellish superior quality movements.


A portable timepiece that functions in all positions.

A watch comprises three essential parts:
• The movement made up of the different mechanical components required to keep the time.
• The case which protects the movement.
• The dial and hands which indicate the time.

A watch can be worn in various ways: pocket watch, wristwatch, brooch watch, etc.


A watch's water-resistance is measured in bars (a unit of pressure where 1 bar equals 1 atmosphere or atm).
Manufacturers generally indicate this water-resistance in metres (m), feet (ft), or atmospheres (atm).
A watch that is described as water-resistant, with or without an additional indication of overpressure, must be conform and tested to the criteria set out in NIHS 92-10 (equivalent to ISO-2281 international standard). These watches are destined for ordinary everyday use, including periods of immersion in water such as leisure swimming. They can be used in conditions of changing air pressure, water pressure or temperature. However, even with an overpressure indication they are not intended to be worn for underwater diving.
A diving watch is made to be worn underwater at a depth of at least 100 metres (330 feet). It must include a time control device and fully conform to the criteria set out in NIHS 92-11 standard (ISO 6425) in terms of luminosity, shock-resistance, anti-magnetism and the solidity of the strap.

Winding mechanism

The mechanism which tightens the mainspring in a watch or lifts the weights in a clock. It comprises about ten parts (see drawing).
The winding and hand-setting mechanisms have nowadays some parts in common.

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