Launched in 1967, the Rolex Sea-Dweller ref. 1665 was developed to cater towards professional underwater divers needing a watch that could withstand deep pressure underwater. While the Submariner ref. 1680 had a depth rating of 660ft (220m), the Sea-Dweller ref. 1665 comes in deep at 2000ft (610m) tripling the ref. 1680.

The Sea-Dweller saw the ingenious addition of a helium escape valve. 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, Rolex worked with a number of divers and organizations around the world to aide in the Sea-Dweller's development, 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.

While early examples of the Sea-Dweller ref. 1665 featured two lines of inscription in red above the depth rating earning its nickname the “Double Red”, later examples featured a dial without the red writing. The present example ref. 1665 “Double Red” from circa 1978 with a 5.2 million serial is belongs to the Mk IV variant with a dotted texture of its red texts. Preserved in attractive overall condition it is also accompanied by its original guarantee and presentation box.