Accompanied by a letter from Jacques Verpeaux, attesting to the original condition of this watch and its provenance, as well as by a file of press clippings and related documents. Rolex Ref. 1665 This reference was made between 1967 and 1978. Rolex carried out extensive examination and testing of the watch following the expedition, at which time it was completely overhauled before being returned to Mr. Verpeaux. However the original mainspring, crown and hands were retained and accompany the watch. T T he Janus IV Operation, organized by Comex, comprised two phases. The experimental phase, took place in December 1976, in Comex?s Hyperbare experi-mental center in Marseille. Comex divers Jacques Ver-peaux, Patrick Raude, Louis Schneider, Philippe Jeantot, Vito Lentini, and John Mac Kenna, as well as two divers from the French Marines, Emile Sevellec and Gérard Vial, took part in tests and exercises inside a sphere filled with water. The pres-sures they experienced were equivalent to those at 430 to 480 meters. The practical phase of the operation was carried out in the Mediterranean, off the coast of Cavalaire in France. The divers were Jacques Verpeaux, Patrick Raude, Louis Schneider, Philippe Jeantot, Emile Sevellec and Gérard Vial. The saturation chambers that they were to live in for the entire operation were slowly pressurized to the pressure experienced at below 430 meters of sea water. Then their vessel, the Petrel, made its way toward the site of the operation. The first diving team was made up of Patrick Raude, Jacques Verpeaux and Gérard Vial. Jacques Verpeaux was the first to dive, going down to 460 meters in the open sea. Gérard Vial followed, then they were brought back up and the second team went down. Over the next three days, several successful dives down to 460 meters were made, during which the divers installed a mechanical and hydraulic subma-rine pipeline, carrying out tests of underwater soldering procedures. On the evening of October 19, 1977, as the divers were resting in their chamber, Mr. Henri Germain Delauze, director of Comex, told them over the loud-speaker how pleased Comex was with the results. He further announced that Comex?s scientific committee had decided to attempt a descent to the never-before attained depth of 500 meters. He asked the six divers if they agreed to try, and all volun-teered to do so. The following morning, Jacques Verpeaux was chosen for the first dive, and Gérard Vial for the second. As they descended, the pressure was brought from that of 430 meters (the pressure of the chambers they had been living in) to that of 490 meters. Jacques Verpeaux made his dive, and the registers on the surface indicated he had reached a depth of -501 me-ters, an exploit never before accomplished. A record had been beaten, and all the sirens of the Petrel and the accompanying boats went off in celebration. Verpeaux smiled for the cameras, then took up a plas-tic slate and wrote ?Janus IV, 500 meters, 1647 feet?. Ten days later, the divers were acclaimed by an overjoyed crowd. The Janus IV Operation was the last diving test made in the open seas using Trimix Helium, which was principally made up of helium, with oxygen and a tiny percentage of nitrogen. It helped deter-mine the limits of human intervention in diving technology. Jacques Verpeaux was thus the first to have made a dive down to 460 meters, and he was the first and only diver ever to have reached the legendary depth of 501 meters. This record, made with the heliox mixture, will most likely never be beaten. Mr. Verpeaux was featured in numerous Rolex Sea Dweller advertisements of the period, and was made Chevalier de l?Ordre du Mérite in recognition of his endeavors on this occasion. The Rolex Sea Dweller No 4196599 was worn by Jacques Verpeaux for the whole diving operation. He had it on his wrist when he reached the unheard-of depth of - 501 meters. Afterwards it was given to him by Rolex in recognition for his participation in the Janus IV operation, and was engraved with his name, the name of the Janus IV operation, and the record depth attained on that occasion. It is thus an exceptional and unique piece on all counts. After having sustained the extreme pres-sures encountered at the depths of - 501 meters (the equivalent of 50 atm), it was nevertheless found to be still in perfect working order.