Cal. 3075 is an automatic watch movement with a fixed central 24 hour hand and date wheel. Only used in the Rolex GMT-Master (Ref. 16750) from 1981 through 1988, Cal. 3075 was very similar to the more widespread Cal. 3035 and the larger Cal. 3000 family of movements. The GMT-Master was updated in 1988 to become the Ref. 16700, with Cal. 3175.
- Rolex GMT-Master (1981-1988), Ref. 16750, 16753, 16758
Compared to the predecessor Cal. 1575, Cal. 3075 was much-improved. The balance speed was increased from 19,800 to 28,800 A/h and it gained a quickset date feature, though it only advances the date wheel. The hacking balance wheel features a Breguet overcoil and Microstella regulation.
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 and 6.2 mm thick, with 27 jewels. It has a power reserve of 48 hours.
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 with the crown in second position (one notch out). Turn the crown counter-clockwise to advance the date wheel by one day.
The time is set with the crown in third position (pulled all the way out). Rotate the crown counter-clockwise to advance the minute and hour hands and clockwise to turn them backward.