I previously owned a Seiko (generation) Gen 1 RAF chronograph from the early/mid 80s, but this is the first time I've ever owned a Gen 2 version. It's been said that both the Gen 1 and 2 watches were issued to RAF helicopter pilots. The Gen 2s came into service in the 90s after the Gen 1s were phased out. The Gen 1s had a different movement (15-jeweled high-end Seiko quartz). These Gen 2s have a no-jewel Seiko quartz movt.
There's a more rare non-luminous dial and hands version of the Gen 2 chronograph that has been linked to RN nuclear submarine crews. The lack of (radioactive) luminous supposedly does not interfere with the radiation detectors on the boat. These non-luminous versions lack the circle-P on the dial and have non-framed hands. (The circle-P denotes Promethium-47 as the radioactive isotope used in the luminous material of the dial and hands).
Finally, there's even a civilian version of the Gen 2 (without issue marks).
All in all this is a very clean piece with some serious wabi in the form of some strap burn. Gotta luv it!
Mine is from 1997 as you can see from the MOD issue engraving.