*Transitional* 1977 Rolex Double Red Sea-Dweller (Ref. 1665) "Mk. IV" W/ Box & Papers

(Co-Branded DRSD Comex/Rolex AD c. 1970's)

In the early part of the 1960s deep-sea diving and in particular, mixed-gas diving was advancing. The Submariner became the quintessential diver born out of the late 1950s, with its iconic design which set the standard for almost all dive watches to come thereafter its launch in 1953. The Rolex SeaDweller was born in the 1960s out of the collaboration with COMEX a French deep-sea diving company. Comex is sometimes referred to as the NASA of the deep seas and was the pioneer in mixed gas diving.

In typical Rolex fashion meaning form following function, most of the SeaDwellers design was born out of the need to comply with the commercial ISO 6425 diving standard, which defines test standards and features for watches suitable for diving with underwater breathing apparatus in depths of 100 m (330 ft) or more. 

Saturation diving requires the use of helium in the breathing gas mixture, and helium particles would accumulate within the case of a diving watch during prolonged exposure meaning long deep dives and or at depths greater than 200 meters/660 feet where mixed brining gas was essential. During the early days of deep saturation diving, a strange phenomenon was arising during the decompression of these dives in which the pressure inside the watch would build as a result of helium gas being trapped in the cases of the watches that were being used. The weakest point of the watch at the time was the crystal and upon decompression from the dives, the helium gas would expand, ejecting the plexiglass crystal as that helium gas forced its way outward. Being that watches back then were crucial tools for timing decompression and other important events this was a major flaw that needed to be fixed. Rolex developed a rather simple and practical mechanism to solve this issue by developing a helium escape valve on the side of the case that allowed the helium particles to escape while still maintaining an ISO 6425 diving standard and water resistance rating.

(Founder Of COMEX, Henri Delauze c. 1970)

 The new model of Submariner was created was dubbed the reference 1665, based on the existing Submariner model with some major upgrades. Initial prototype models were exclusively issued to DeepSea Explorers of the 1960s in various configurations but in the late 1960 and early 1970s, the model made it to the Rolex retail stores.  The Double Red Sea-Dweller (DRSD) was produced for approximately 10 yrs starting in 1967 to 1978 with serial number range 1.7 to 5.2 million. There were four different dial variations made in the regular production model with three different case back configurations. Post 5.2 million serial number ref. 1665 Sea-Dwellers can be seen only bearing white text and have earned the nickname, "great white" Sea-Dweller.

The Sea-Dweller is undoubtedly the most advanced amongst the diving watches of its time. Featuring a bidirectional bezel, a tropic super domed bezel to withstand greater pressure, and date a complication. Fully certified and guaranteed waterproof to 2000ft - 610m.

The Mk. IV Double Red Seadweller dial possesses the following key characteristics

• Closed 6's in the depth rating
• The top line of red text (Sea-Dweller) is much larger than the bottom line of red text
• The coronet is large with clearly defined spikes and the opening of the coronet is large.

This exceptional and complete ref. 1665 is an extremely transitional example and is best known as being the very last series of the double red dial ever produced by Rolex. Featuring a correct serial number of 5.2mil, this transitional piece sets itself apart with "round text" displayed on the case back which is almost exclusively seen in the later "Great White" ref. 1665 Sea-Dwellers.