Atmos

A clock, made by Jaeger-LeCoultre, driven by variations in temperature or atmospheric pressure and invented by Jean-Léon Reutter. The original Atmos, made in 1926, was presented to...

Brilliant cut

A round diamond that is cut with 57 or 58 facets or 32 facets + plus the largest facet called the table, 24 are below. The 58th facet is optional and is polished at the point of the diamond.

Case

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...

Daylight Saving Time

Legal time in certain countries that is one hour ahead of winter time, itself one hour ahead of solar time.

Exterior

The different parts (case, dial, hands, crystal, crown, etc.) that help to give the watch its finished and functional appearance.

Foliot

An oscillating bar with a weight at each ends used as a regulator in the first mechanical timepieces.

Gold

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,...

Horn

That part of a watch case to which the strap is attached. Horns come in various shapes and are attached to the case middle.

Isochronal (Isochronous)

Recurring at regular intervals. The oscillations of a pendulum or balance are isochronal when their duration is the same regardless of their amplitude.

Knot

A raised mineral inclusion in a diamond found at the surface.

Legal time

The time which is, by law, that of all the inhabitants of a country.

Manufacture

The Swiss watch industry uses this term to differentiate between a company that manufactures a watch almost in its entirety as opposed to finishing shops which only assemble and time the watch,...

Niello

An enamel-like alloy of lead, copper, silver, sulphur and sal ammoniac (ammonium chloride). Niello paste is applied over incised gold or silver then fired in the enamellist's furnace. Excess...

Onyx

A black agate that is often found as watch dials.

Poinçon de Genève

A distinctive hallmark depicting the Geneva coat of arms, granted by an official body at the Ecole d'Horlogerie de Genève and placed on movements whose quality and finish conform to precise...

Quartz

Silicon dioxide. Also called rock crystal. Quartz has the specific property of vibrating at a very high frequency (32 MHz) placed under electric current. Under certain conditions, it...

Repair

To restore a watch to a functioning state.

Set (to)

To secure a stone of any cut or size in metal. The stone and the metal are generally precious. The jeweller prepares the hole in which the stone is seated.

Tooth

A projection on the edge of a gear, escapement wheel, ratchet wheel, etc.

Ultra-complicated watch

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...

Vibration

Movement of a pendulum or oscillating body between two extreme positions (A' and A''). The balance of a mechanical watch generally makes five vibrations per second, equivalent to 18,000...

Watchmaker's cabinet

A small chest of drawers for storing the watchmaker's tools and often part of the bench. A cabinet can also be a separate piece of furniture with any number of drawers for sorting and...

Year

A four-digit indication of the current year that changes automatically at midnight on December 31st.

Zinc

A metal applied by electrodeposition (electroplating) to protect iron and steel.