From 1983, the standard Royal Navy issued dive watch switched to a quartz movement. However, there also exists a mechanical automatic dive watch bearing 1984 issue markings, and produced in a batch of 100 watches (from observed case back issue numbers). These are generally thought to have been a special order for a British military unit in Hong Kong, as many have been found in Hong Kong or nearby countries (hence the "Hong Kong Special" nickname).
The watch does not look like any of the other 1980s CWC dive watches; it is in a different style case and is of a notably lower quality, the logo on the dial is a strange variant of the previous sans-serif logo but in an oval, and the movement is different to the ones used in 1980 and 1981.
The handset is similar to the 1980 dive watch, and the dial has a very small circled T below the central pinion and luminous numbers 3, 6 and 9, both features only found on the 1980 dial made by Dodane.
The case is an Airain France case - which is another brand name owned by Dodane - and a Dodane family member appears to have confirmed that they made "CWC" watches in 1980 and 1984. Airin also produced a civilian version of this watch.
Given how different this watch is from all other CWC dive watches, there has long been debate about whether this watch was actually supplied by CWC. Ray Mellor was categorical that CWC did not supply the watch. "It’s obvious - if the movement is somebody else’s or one that we’d never used, the case is made by a casemaker who knew us but didn’t necessarily know what it was being used for, and if the dial is marked with CWC not by us, then it’s a fake!"
The evidence strongly suggests that this was an order fulfilled by Dodane, trading on the fact they made the original 1980 diver, but was never actually a CWC watch.
The 1984 "Hong Kong Special"
The 1984 watch (bottom) compared to a 1985 watch (top). Note the multiple differences: case shape; lug width; logo; handset; bezel insert; quality of lume; circled T...
The AS 1479 movement in the 1984 dive watch. The 1980 and 1981 automatic dive watches used ETA movements.
Case back of the 1984 watch; this is not a case back seen on any of the other CWC dive watches, and the NSN and issue numbers are very lightly engraved. The serial number starting 139xxx also changes with each watch, but not in sequence with the issue number, so they were clearly added at different times.
Detail of the case back showing NSN of 6645-99 9237697 for an automatic dive watch and issue number 27-84.
One dial variation sometimes seen is this one with an open 6 and 9; a few of these have been seen, but I believe these to be a redial by a Hong Kong watch dealer. The logo and circled T are different from those originally produced by Dodane, and no other CWC watch has ever been seen with an open 6 and 9 like this.