Rolex

The model that succeeded the 1665 was launched in 1978 as the 16660 affectionately known as the "Triple Six".  This model was a big leap as it had a depth rating of 4000 feet as opposed to the predecessor with only 2000 feet model 1665. The Sea-Dweller 4000 was the result of the partnership between Rolex and the commercial deep sea diving company COMEX. Rolex developed a helium gas release valve for their needs and was used by the COMEX divers since 1992. The Sea-Dweller 4000 is powered by the same COSC certified Rolex 3135 automatic winding movement that is used on the Submariner. Originally with a 3035 movement (16660)  changed late 80's to the  3135 movement which is perfect for what it was intended,  solid work horse, accurate mechanical movement with no complications (apart from date).  It features a scratch resistant sapphire crystal, unlike the previous 1665 which had a domed plexi and an improved, larger helium escape valve.  The watch was designed to feature a glossy dial with metal circled index as in current model 16600.  But as we all know Rolex never leaves any dials to waste on the shop floor so the early model 16660 featured the matt dial with painted index markers. I am guessing the painted dials ended around 1987/88ish.  This is the model that can currently be found on the market but has been discontinued by Rolex which has replaced it with the DEEPSEA.  The DEEPSEA, official depth rating of 3,900 meters (12,800 ft) with a 44mm case diameter (48 mm with crown) and being 18mm thick it is a much heavier piece than the original. 

The Sea-Dweller 4000 is assured a place in history as a classic modern Dive watch, a look perfected by Rolex, for decades to come.

Please feel free to make corrections, add omissions and post your Sea-Dweller.

Bill