Technical review of Rolex Sea-Dweller 1665 MK IV "Double Red"

This reference boasts a rich history full of anecdotes, and a comprehensive article on the 1665 would be quite lengthy. Therefore, we have chosen to feature the MK IV from 1977 in our "Around My Wrist" / 41Watch Vintage section.

The depth capacity of this reference has always impressed diving watch enthusiasts. Why create a watch capable of descending to 610 meters when an average diver is entirely unable to reach such depths? With the world record for scuba diving being 330 meters and 675 meters with a competition diving suit, it is clear that this diving tool was not intended for public use at its maximum capacity.

This watch was actually developed by Rolex in collaboration with the Compagnie Maritime d’Expertise (COMEX) for deep dives inside bathyscaphes. Its distinctive feature, apart from its ability to reach 610 meters, is that it was equipped with a helium valve. This allowed the watch to release helium used during deep dives, enabling the diver to breathe at extreme and dangerous depths for the human body. The patent was filed in 1971, and Rolex simply decided to make this genuine tool available to the general public.

Over time, the models have evolved, mainly in the dial design and the thickness of the watch case.

The model presented here is a 1977 MK IV, with a thick case and double red dial, the last of its production run, as subsequent dials were fully marked in white.

The characteristics of the MK IV are as follows:

Case: Thick

Bezel: Graduated “Fat Font” serif

Dial: Manufactured by Lemrich & Cie with a grainy print effect on the markings. Closed “6” in 610, with a very open and thin crown

Case Back: Two versions, the first likely sourced from MK III stock, with the date under the reference, and the later versions with the reference only and no date indication.

Movement: Modified Caliber 1570 (since 1971), running at 19,800 bph and equipped with the stop-seconds function.

Undated case back	Very open and thin crown

This watch is a collector's item par excellence and highly appreciated by brand purists.