The launch coincided with another impressive Rolex diving feat. On Jan. 23, 1960, the submarine Trieste, with its 2-meter-wide pressure sphere, big enough to hold two people, descended for the 65th time into the depths – this time with the goal of reaching the Challenger Deep in the Mariana Trench, the deepest point in the ocean. Inside the pressure sphere were Piccard’s son, Jacques Piccard, and the American Marine lieutenant Dan Walsh. Outside the sphere was a very special Rolex prototype, a watch, with Oyster case, designed to withstand the pressure of the 10,916-meter descent, which exerted a pressure on the vessel of about 1,125 kg/cm. The idea, of course, was to prove that the Oyster case could survive the ordeal.
Excitement was great when the sphere resurfaced after its triumphant dive. How would the watch look? Would the hands still show the correct time? Just as with the 1953 Bathyscaphe dive, the Rolex emerged unscathed. It looked and ran exactly as it had above the water.
Later that decade, Rolex introduced a new dive-watch feature. It was designed to solve a problem that had emerged as a result of the introduction into professional diving of breathing gases that blended oxygen and helium. These gases enabled divers to descend deeper than before. But divers who wore their watches in decompression chambers filled with the new gas mixture often faced a rude surprise. Helium molecules penetrated the watch crystals and seals and entered the watch cases, and when the pressure in the chamber was reduced during decompression, the helium gas that had built up inside the watch was unable to escape quickly enough, so the watch crystal popped off the watch like a Champagne cork.
Among the divers using these new gas mixtures were those employed by the French company Compagnie Maritime d’Expertise (Comex). Comex worked with Rolex to find a solution to the popping-crystal dilemma and in 1967 Rolex patented a valve that allowed the dangerous buildup of gas to escape easily. At first Rolex used the valve in standard Submariner models (Ref. 5513). A modified version was produced in Geneva solely for Comex. It bore the Comex name on the dial and a special identification number on the back. The second signed Comex series was given its own unique reference number, 5514.