Basing on the calibre Rolex 3135, additional GMT indication (dual time zone). Further development of the Calibre Rolex 3185 with Parachrom blue hairspring and quickset date feature. Used since 2005 in late examples of the GMT-Master II Ref. 16710 and replacement GMT-Master II Ref. 116710.
Cal. 3186 was also used in the Explorer II, Ref. 16570 from 2007 through 2011 until the larger 42 mm Ref. 216570 was introduced. This featured the wider-diameter Cal. 3187 to better situate the date window in the dial.