Seamaster Planet Ocean 600M

39.5?mm, steel on leather strap

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).

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.

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.)

A series of watches whose production run is determined in advance of production and limited to a set number.

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

A transparent caseback – 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.