No European proof marks from pressure testing. Not sure it ever went over...
Indeed, as Kevin says, it is a perfectly normal L-L British Service Model with exactly the markings you would expect.
Contrary to popular misconception, the British did not apply any government/military proof marks or property marks to these before they issued them; only those were proofed commercially that had been surplused out in Britain for civilian sale post-war, which obviously did not happen to this one.
It could have been a private war bringback or assigned to a Commonwealth country other than Britain.
The only truly odd thing is its state of preservation, considering the low serial from late 1942. It appears unissued except for storage blemishes. That, together with not retiring through normal channels, might indeed indicate it was diverted from service early in its career, possibly in an irregular fashion, here or in Britain.
Of course, it could have also just been issued to some desk-bound officer and spent the war in a drawer, not getting turned back in, and making its way back here through private channels.
Speculating can provide endless fun
