The Rolex Deep Sea Special No. 3 is the experimental watch believed to have been strapped to the outside of the bathyscaphe Trieste when it reached the bottom of the Challenger Deep in the Mariana Trench on 23 January 1960. It is a prototype rather than a production model: an Oyster case with a white dial and an enormous domed crystal, described as many times larger than on a normal Rolex and taller than the glass of the earlier No. 1. Its caseback is engraved “ROLEX OYSTER / NO. 3 / DEEP SEA SPECIAL”. The early prototypes used the hand-wound calibre 1000. The dive reached a depth usually given as 10,916 m, while Rolex’s own 1961 advertising and the later display models use 10,908 m. It matters because it proved that a watch case could survive the deepest point of the ocean.

Rolex began testing Deep Sea Special prototypes in 1953 on the Trieste, reaching 1,080 m and then 3,150 m off Ponza Island on 30 November 1953. For the 1960 record dive, piloted by Jacques Piccard and Lieutenant Don Walsh, a later prototype was fixed outside the hull, and Piccard sent a telegram confirming the watch had gone 11 km down. Only a handful of prototypes are known: No. 3 with a white dial, and No. 1 and No. 5 with black dials. After the dive Rolex made numbered commemorative display models, the first of them No. 9, engraved with 10,908 m and 35,789 ft; later examples such as No. 35 of 1966 carry the calibre 1570.

The Deep Sea Special is one of the most celebrated objects in Rolex history and in diving history. Prototypes and display models fetch high prices: Christie’s sold No. 1 in 2005 for CHF 322,400 and No. 31 in Hong Kong in 2009 for 438,000 US dollars, and Phillips offered display model No. 35 with an estimate of CHF 1.2 to 2.4 million. Collector writers note gaps in the record, including uncertainty over how many prototypes were made. No. 3 itself was never produced for sale; it is held by the Smithsonian’s National Museum of American History in Washington, D.C., where it has been kept in storage rather than on display. Rolex continued the deep-diving story with later experimental watches, including the Rolex Deep Sea worn by James Cameron on his Deepsea Challenge dive.