The release of the popular replica Rolex Sea-Dweller last year – with its single line of red text – brought a large number of focuses back towards Rolex’s line of deep-sea, saturation diving watches. Even though the helium gas escape valve has become the defining feature of the Sea-Dweller line, the very first fake Rolex model to be full of it was actually a Submariner that was used as prototypes while Rolex worked with the French diving company, COMEX, to upgrade the design of their gas release valve. 
All early examples of this fake Sea-Dweller were originally equipped dials with red text on them; however, as for the amazing vintage Sea-Dweller watches, a dial with one line of red text is not the same as a dial with two lines of red letters.
The very first watches to bear the “Sea-Dweller” name were the prototypes that were used for field-tests during the early Tektite projects, in which divers would spend multiple days living in a pressurized chamber below the surface of the ocean. These fake watches have both the “Submariner” and “Sea-Dweller” names printed on their dials; however, on these early prototypes, it is only the Sea-Dweller name that appears in red letters. What’s more, next to the Submariner name, a depth rating of “500 M – 1650 FT” is also printed in white text.
It’s very funny to see that many of these Single Red Sea-Dweller watches did not have helium gas escape valves, since the issue with trapped helium molecules only occurs at greater depths when divers are living in helium-saturated environments for extended periods of time. Different from the modern Sea-Dweller 126600 which is mass-manufactured, only about a dozen of these watches were ever made, and all were given to divers that had been handpicked to receive them for either testing purposes or as awards. Due to how few were ever manufactured, Single Red Rolex Sea-Dweller replica watches are extremely rare and command unbelievable premiums whenever they manage to surface at auction.
When the fake Sea-Dweller was first launched to the public, the fake watch was originally fitted with a dial that still had red lettering; however, it was the addition of a second line of red text that separated it from the small batch of prototypes that had come before it. These “Double Red” Sea-Dweller watches have the names, “Sea-Dweller” and “Submariner 2000” printed on their dials in red text, below which, a depth rating of “2000 ft = 610 m” appears in white.
The Double Red Sea-Dweller was made for roughly the first 10 years of the fake watch’s existence; however, some of these replica watches have their original “Double Red” dials replaced with later-era equivalents that feature all-white text and do not have the “Submariner 2000” name printed on them at all. Even though they are becoming quite hard to find in all-original condition, Double Red Sea-Dwellers are actually more common than the prototype Single Red Sea-Dweller watches that preceded them.