Cal. 3085 was the first Rolex movement with an independently-adjustable GMT hand. Introduced in 1983 in the GMT-Master II, the movement measured 6.3 mm thick, giving that watch the nickname “Fat Lady”. It was a short-lived movement, with the thinner Cal. 3185 introduced in 1988.
- Rolex GMT-Master II (2003-2008), Ref. 16760
- Rolex Explorer II (1985-1988), Ref. 16550
It is a 28,800 A/h 12.5 ligne movement with bi-directional automatic winding and chronometer certification. The movement is 28.5 mm in diameter, with 27 jewels. It has a power reserve of 48 hours. Although some sites claim that the height or thickness of the movement is 6.3 mm, the official Rolex parts diagram lists it at 7.20 mm.
The movement can be manually wound with the crown in position 1. Rotate the crown clockwise to wind the mainspring.
The date wheel is advanced along with the independent 12 hour hand, forward or backward, with the crown in second position (one notch out). Set the hour hand to the local time and date, leaving the 24 hour hand showing “home time”.
The time is set with the crown in third position (pulled all the way out). Rotate the crown clockwise to advance the minute and hour hands and counter-clockwise to turn them backward.