A quite nice Supersport turned up, old enough to have the single stage plastic trigger blade, and not have the Anti-Bear-Trap of the later versions.
To my somewhat limited knowledge, this places the rifles production date somewhere before 2000, as my dad bought a Lightning new around 1999, which had the ABT.

Now, the big mystery is that I cant find the serial number. I own several Lightnings, Supersports, Tacticals, and meteors from mk1 up through mk6, so I know that the serial number has been moved around a bit. But this gun totally lacks a serial number
Never seen this on a BSA before, if anyone can shed some light on this I would be happy for the info!