The ‘Single Red’ Sea-Dweller, reference 1665, was the watch that started the lineage of one Rolex’s most important professional tool watches. The very first ‘Dweller was a prototype that was issued to professional divers to test in the field. The most interesting aspect of these watches was that they were not equipped with gas escape valves.
Rolex were experimenting with watches that could operate at much greater depths and so the prototype 1665 was depth rated to 500m/1650 ft. Recent research has suggested that there were ten of these watches made. Of the ten, seven were given to the underwater explorers who took part in the first Tektite project.
Tektite was an innovate experiment to build an underwater habitat in which the first aquanauts would live; which they did for 58 days — a record at the time and the perfect extreme test for the prototype Sea-Dweller.