The Sea-Dweller model was launched in 1971. It is the first diver's watch with a Rolex patent valve in the band and guaranteed waterproof to 610 meters depth. The valve was first developed on the Submariner model and allows helium and other gases to escape, enabling the watch to stand compression. The first Sea Dweller model with red printing and 'Submariner 2000' on the dial is a version of the Submariner model and was discontinued in 1973.
The present watch is from the second series with the revised form with white printing on the dial and without the 'Submariner 2000'. It is pressure-proof to a depth of 2000 feet or 610 meters.
An example of reference 1665 is illustrated in The Best of Time - Rolex Wristwatches by James M. Dowling & Jeffery P. Hess, p. 269.