If this were a 1943 Long Branch sniper, it would be a pre-
BATCH production model, would not expect to be for export, would be mounted with an REL #32 Mk 1 scope, should have the scope serial number (usually 1-3 digits, prefix or suffix of "C" on the butt heel (I've seen both), mount not necessarily
FULLY serialed to rifle (at this time).
BATCH production of the LB T began in 1944, but as stated either 71 or 73 were known to have been produced
BY DEC 31, 1943.
I know of no original Long Branch "T"'s mounted with British
scopes; none show up in my serial number list. Your serial number is close to known 1943 LB snipers. Interesting, no doubt. As an aside, from my studies, no REL scopes were over three digits.
Mk I, Mk IA and MkII scopes appear to run in consecutive serial numbers, MkIII and Mk4(No.67) scopes each have seperate serial ranges started over at "1" with each mark, and there were 3 or 4 marks, it's late and I can't remember.
My .02c.