Rolex Explorer II

Introduced in the early 1970s as model 1655, it is essentially a GMT-Master with a fixed bezel. Using the same calibre 1575 movement as a GMT- Master, it also had a fourth hand which rotated once every 24 hours, however on the Explorer II the hour was read from this from a fixed, engraved 24 hour steel bezel. The watch was introduced as being especially useful for the speleologist ( or cave explorer), who, Rolex claimed "soon loses all notion of time: morning, afternoon, day, or night. " For these intrepid souls Rolex developed the watch which would tell them whether the "2" on the dial was 2:00 a.m. or 2 :00 p-m. (14:00 hrs). This may well be true, and perhaps cave dwellers are more susceptible to losing track of time than others. We would suggest, however, that the demand for a watch specifically targeted at speleologists would find a tiny market, and that even its limited popularity was due to its acceptance by others who work in civilian and 24 hour time systems, such as pilots and air traffic controllers. The watch went through two styles. The first, made for only three years, used an orange 24 hour hand, and the following model, made until 1985, used a red one. The 1655 Explorer II and the 1019 Milgauss are the only Rolex models which use hands that are used by no other model.

We used the phrase "limited popularity" above intentionally for this watch always was one that was never very widely distributed. It was not really popular until 1991, five years after it was re-launched with a sapphire glass and the same movement as the GMT-Master II. 
This allowed the owner of the watch to set the hour hand backwards or forwards in one hour jumps without disturbing the second and minute hands. This facility allowed the owner to change time zones without losing a pre- set accurate time.

The new watches, like the first model Explorer II's had the bezel numbers enameled in black, but the very first of the new model Explorer lls had very unusual red bezel enameling. These early white dial models had the tritium dots and the hands out- lined in white gold, while the following models had them out- lined in black.

The name, Explorer, and its whole history of promotional material have made much of the watch's ability to resist hazards and we are sure that this reflected glory is the reason for the watch's continued popularity.