The Sea-Dweller is now one of the most appreciated Rolex timepieces, possibly because of its genesis as one of the ultimate tool watches, born out of true necessity and grown to become an iconic piece of watchmaking. Its history begins in the mid-1960s. At the time, a number of international experiments were developed with the goal of demonstrating the possibility of living for an extended period of time (sometimes weeks) in underwater habitats. Rolex began developing timepieces which would resist very deep dives, and underwater habitat conditions where a pressurized mixture of helium and oxygen was used for breathing.

The helium escape valve was an ingenious invention because when working in helium-rich atmospheres, tiny helium molecules would seep through the crystal and rubber gaskets into the watch and create pressure once the diver had surfaced. This would usually result in the crystal popping off. The development of the valve was meant to prevent this issue by letting the gas escape the watch case and easing the pressure. Today, it is well established that Rolex worked with a number of divers and organizations around the world to aide in the Sea-Dweller's development. For example, the scientists of the American underwater habitat, Tektite, wore such watches in 1969 and 1970, and the same is true for the scientists working at the Sealab III experiment. The name Sea-Dweller itself is a direct nod to the fact that the model had been developed to meet the demands of scientists living - or “dwelling” - under the sea. Following the positive results obtained with these companies, Rolex went on to publicly commercialize the model.

The earliest iterations engraved with “Patent Pending Rolex Oyster Gas Escape Valve” on their casebacks (such as the present example) are highly sought after. These early models were in effect prototypes, and their caseback interiors feature the last three digits of the watch’s serial number - stamped 440 on the present example, as well as IV.67 indicating production in the fourth quarter of 1967. The Mark 1 dial is a second defining feature of these prototype models; the double red printed Sea-Dweller on the first line, and Submariner 2000 on the second – all words in an equal font size. The vividness of the red color found on the present example is especially noteworthy since these designations consisted of the red print placed on top of white, that over time, would often fade to a light pink tone. Almost as exceptional as the history and rarity of this piece is its well-preserved condition, with thick chamfers on the lugs and a sharp case.