Extremely rare, the Deep Sea Special was nonetheless an extremely important development for Rolex, helping to spur further development of the Submariner and Sea-Dweller lines. Its development dates back to the early '50s when Rolex decided to move beyond simple waterproofing and create tool watches for divers. As part of this push, it enlisted Swiss oceanographer Jacques Piccard to help test various prototypes. This culminated in the watch reaching a depth of 35,789ft while testing in the Marina Trench. That watch, and most other examples, are in the hands of science, technology, and watch museums, making this particular commemorative watch only the sixth such example to become publicly available. Made in 1965 and numbered 35, it will be sold by Phillips during its Geneva Watch Auction: XIV in November.