45.5 mm, steel on steel^OMEGA Best

Anti-magnetic

The movement is unaffected by exposure to strong magnetic fields, even those greater than 1.5 tesla (15,000 gauss).

Chronograph

The chronograph function is a mechanism for measuring time intervals. A chronograph watch can therefore be used to time events while displaying the time like any traditional watch.

Chronometer

Label given to a watch which has undergone precision tests and received a certificate from an official body (COSC).

Date

The day of the month, displayed in a window on a watch dial at the 3 or 6 o’clock position, or within a subdial at 9 o’clock.

Helium escape valve

Decompression system which allows helium to escape from inside the watch when the watch is worn for professional use in pressure chambers. (Long-term underwater work, crude oil exploration, etc.)

Master Chronometer Certified

Guaranteeing the Swiss industry’s highest standard of precision, performance and magnetic-resistance, as set by the Swiss Federal Institute of Metrology (METAS).

Screw-in crown

Self-locking crown, screwed into the tube of the case, used for highly water resistant divers’ watches.

Small seconds

A hand on a sub-dial which tracks seconds typically it completes a full rotation in one minute.

Time zone function

Allows the hour hand to be easily adjusted to different time zones without stopping the watch.

Transparent caseback

A transparent caseback – frequently made of sapphire – makes it possible to see the movement inside the watch.

Unidirectional rotating bezel

A bezel which turns in only one direction. Particularly useful for divers who cannot accidentally rotate it in the wrong direction, which could cause them to miscalculate their dive times. A rotating bezel makes it easy to measure elapsed time.