Cal. 3185 was an automatic movement with date and independently-adjustable GMT hand. Introduced in 1989, it replaced the short-lived Cal. 3085 in the Rolex Explorer II and GMT-Master II models until it was replaced by the updated Cal. 3186 around 2005.
- Rolex Explorer II (1989-2006), Ref. 16570
- Rolex GMT-Master II 16710 (1989-2005), Ref. 16713, 16718, 16750
Cal. 3185 used a simple ratchet on the hour wheel to advance the date. This was changed for the successor Cal. 3186, which has a click spring in its place. This change eliminated the characteristic “wobble” of the 24 hour hand when adjusting the time but has also proven to be less reliable. Cal. 3186 also features a Parachrom blue anti-magnetic hairspring in place of the Nivarox used on Cal. 3185.
One major upgrade for the 3100 family was the use of a full balance bridge rather than the simple balance cock used previously. This added stability and durability to an already well-respected movement. The balance is made of the advanced beryllium/copper alloy known as Glucydur and uses Microstella regulation using four screws inside. The balance uses a Nivarox hairspring, the only component not produced in-house by Rolex, and features a Breguet overcoil laser welded to the balance stud. The automatic winding gears, coated in PTFE, are deep red colored, and the rotor uses synthetic rubies rather than ball bearings. Most 3100 movements still use the Kif Elastor anti-shock system on the balance.
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.