Probably one of the most rare, and therefore desirable, Rolex watches is the Rolex COMEX Submariner. Designed for the professional diver in the late 1960s following a commission by Compagnie Maritime d’Expertises (COMEX) the first prototypes were released between 1969 and 1971 and given the model number 5513.
The main issues which Rolex had to overcome in the design of the COMEX Submariner were the extreme depth water resistance and explosive decompression caused by helium getting inside the watch. The fix? A helium escape valve. Situated at the nine o’clock position this helium escape valve slowly released the pressure, maintaining a balance with the atmospheric pressure. Whilst this did allow divers to wear the watch at extreme depths the original Rolex 5513s were still just a prototype design and the valve tended to wear out due to oxidation. As a consequence, and once the trial period was complete, an improved Rolex COMEX Submariner with smaller valves made from stainless steel was produced, which fixed the oxidation issue. These versions were given the model number 5514.