The Enfield sales ledgers show that rifle 502 was one of 31 Enforcers purchased by the Northern Ireland Police Force.
No502 was shipped on the 24th March 1977 under advice/inspection note number 430396/1
(It appears to have been a 'standard' Enforcer when it left Enfield).
I wonder if it had been 'played with by a civilian owner making a 'wannabe L42A1' - or, did the local Police Armourer 'acquire' a load of L42 parts (How ?) and make himself an L42A1 'look alike' ?
If you are looking to buy - buy it for what it is, not what it is alleged to be.