The Rolex Sea-Dweller was developed specifically for professional divers who required a robust timing instrument that could withstand their gruelling working depths, as well as cope with decompression as the diver made their way to the surface. Specialist measures were put in place, including the helium escape valve to allow for escaping gas, and a heavy domed crystal. Following the success of this model, in 1967 Rolex launched the reference 1665 in further series, which was the first wristwatch designed especially for saturation diving. So rushed was the launch that the final approval for the patent of the helium valve had not been granted, as such we see the case backs engraved with ‘patent pending’.
Seven dial variations and three case back configurations can be identified over the ten years the model was in production. This wonderful example is one of the last models in production with a type IV dial.