Rolex

This exceptionally rare stainless steel prototype wristwatch, reference 1665, represents a pivotal chapter in the history of Rolex, being instrumental in the development of the now-iconic Sea-Dweller and its pioneering Helium Gas Escape Valve (HEV). It was employed by commercial divers during the late 1960s as part of rigorous testing and development to meet the increasing demands of deep-sea exploration.

The tonneau-shaped, three-body case features a 40mm diameter and is notably slimmer than later production models, reflecting its prototype origins. Equipped with the revolutionary Helium Escape Valve, this model was designed to release accumulated helium from the case during decompression, a key innovation that cemented Rolex’s reputation in the field of professional diving instruments. The outer case back bears the coveted “PATENT PENDING” engraving, with the inner case back dated to 1967.

The rotating bezel, with a black insert calibrated for the first 15 minutes, is a signature feature for dive watches of this era, while the domed plexiglass crystal, Tropic 39, enhances its robustness. The watch is fitted with a Rolex reference 9315 stainless steel bracelet, featuring the rare patent pending diver’s extension link, ensuring a secure fit over diving suits.

One of the most striking aspects of this prototype is the dial. Originally matt black, the dial has developed a mesmerising tropical patina, fading into a rich brown hue that is especially prominent around the centre and the date aperture. This naturally occurring transformation lends the watch a unique and captivating character, highly prized among collectors. The luminous tritium markers remain intact, and the words “SEA-DWELLER” and “SUBMARINER 2000,” printed in red, retain their vividness, a distinctive hallmark of early Sea-Dweller models. The depth rating of 2000 FT/610 M is printed in white below the red text. The steel “Mercedes” hands, with tritium coating, maintain exceptional legibility even in low-light conditions.

Powering this exceptional watch is the self-winding chronometer calibre 1575, featuring a monometallic balance and 26 jewels, with movement number D54861. This movement is celebrated for its precision and durability, crucial attributes for a timepiece designed to perform under extreme pressures.

In all, this Rolex Sea-Dweller prototype is not only an exquisite collector’s item but also a piece of horological history. Its rare combination of pre-production features, remarkable condition, and the heritage of its role in Rolex’s pioneering underwater technology make it a highly desirable and historically significant example of fine watchmaking.