Dial, case and movement signed. DIAM. 40 mm. THICKNESS 15 mm. Approx. overall length 195 mm. The Rolex Sea-Dweller is one of the most purpose-fully designed watches that Rolex has ever made, and possible the most important diving watch of the second half of the 20th century. Born from a collaboration with various diving professionals, governmentally agencies, and Rolex, the watch was the first to introduce the idea of the helium gas escape valve. This valve solved the problem of achieving deeper dives while maintaining the functionality and integrity of the watch. As an ongoing development, the Ref. 1665 Sea-Dweller saw many revisions and iterations with the most coveted being the very earliest examples. The watch offered up for auction here is one of those pieces. Never seen at auction before, including this particular example, there are 6 known examples of the "Single Red". The moniker is given for its one line of text on the dial, "SEA-DWELLER". It is unique from other examples of the 1665 as the DEPTH rating on the dial is 500m instead of the more common 600m. The dials also have a very rough and prototype feeling about their printing as the "DATE" in Oyster Perpetual DATE is much larger and seemingly added to the text as an afterthought. The luminous material on these watches also looks to be hand applied and many still glow, which is an attribute usually associated with the latest production gilt dial sports watches Rolex made in the late 1960s. These watches generally come in two configurations. The earliest ones have no helium gas escape valve, nor engravings on the outside of the caseback to denote this. These were the very first examples that were given by Rolex to commercial divers to test in the field. The subsequent ones that did have a gas escape value fitted had an identical dial, but also bore a hand- engraving along the lip of the case that reads "OYSTER GAS ESCAPE VALVE PATENT PENDING". This is very different from later examples (Including standard Patent Pending Ref. 1665s) as the engraving is done by hand and looks much more rough and hand made as opposed to being machined. The most significant and important example would be this one, which can be argued is the very first watch Rolex made of the Sea-Dwellers. These watches truly were the prototypes for subsequent production models of the Sea-Dweller. Their history, intertwined with the lives and contributions of important divers of the 1960's make them one of the most historically significant watches that Rolex ever made, and thus one of the most important dive Rolexes to have ever come for auction. A truly superlative example in rarity and condition.