Thanks to its reference number, the Rolex Sea-Dweller 16660 is affectionately known among collectors as the “Triple Six”, which we call a transitional reference. Rolex first introduced the Sea-Dweller ref. 16660 as the second model to join the saturated dive watch collection launched by Rolex in 1978. It bridges the gap between the previous Sea-Dweller 1665 and the subsequent Sea-Dweller 16600, with design details from both generations. With this in mind, it is important to note that replica Rolex produced both the Sea-Dweller 1665 and the Sea-Dweller 16660 for approximately five years. 
The reference 16660 is an important model in the history of the Sea-Dweller because it brought some key changes to the watch, such as new crystal materials, a new movement, a quickset date function, and double the water resistance. The youngest Sea-Dweller 16660 is now more than 30 years old, which means the “Triple Six” is technically a vintage Rolex watch. However, at one point during the watch’s decade-long production run, Rolex updated the dial from matte to glossy with applied hour markers. As a result, the early Sea-Dweller 16660 appears more vintage in style than the later versions. If you’d like to add this classic Rolex tool watch to your collection, or just want to learn more about it, go through our ultimate Rolex Sea-Dweller 16660 guide to learn more.
Rolex Ref. 16660 “Triple Six” is the first Sea-Dweller watch with a sapphire crystal protecting the dial, replacing the domed Plexiglas crystal of the old Ref. 1665. Of course, the sapphire crystal is now standard on all Rolex watches, especially for its resistance to scratches. Like all versions of the Sea-Dweller (until the latest version released at Baselworld 2017) the sapphire crystal of ref. 16660 does not include the Cyclops magnifying glass above the date window. Since all other fake Rolex date models include the Cyclops lens, this is a design detail that sets the older Sea-Dweller watches apart from the rest and is appreciated by many.
In addition, the Sea-Dweller 16660 is equipped with a larger helium drain valve. New crystal materials and a larger HEV, combined with a slightly thicker case, make the Sea-Dweller 16660 water-resistant. The “Triple Six” Sea-Dweller is water-resistant to 4,000 feet (1,220 meters), twice as much as its predecessor.
The new design of the Sea-Dweller 16660 also includes a unidirectional bezel instead of a bidirectional one – a safer option for divers, as it is far better to overestimate immersion time than to underestimate it.
Like many of Rolex’s vintage models, the Sea-Dweller ref. 16660 comes in a variety of dial variations. Regardless of the production date, they all have one thing in common: tritium luminescence, Mercedes-style hands, and black background with white text.
Following the matte dial, Rolex equipped the Sea-Dweller ref. 16660 with a glossy black dial with white gold surrounds on the hour markers. The first of these glossy dials (Mark III) actually has two interesting details. The first is that the hyphen between “SEA” and “DWELLER” is no longer included. The second is that these new glossy dials had a flaw that caused many examples to crack (known among some vintage collectors as “spider dials”).
Rolex fake watches corrected this situation and offered a second version of the glossy dial (Mark IV) without the cracking problem and with the hyphen restored from the Sea-Dweller name. The crown was also slightly elongated and the font slightly changed. It is worth noting that some of the once glossy dials are turning matte over time. Unsurprisingly, this has now attracted the interest of vintage Rolex collectors around the world.
