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

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

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.)

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

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

A transparent case back - frequently made of sapphire - makes it possible to see the movement inside the watch.

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.