Thanks Res. In fact it looks like the original rifle serial number of AK 5018 would make it a 1943 BSA. The bracket has been fettled up in the past - the cradle serial numbers have been re-done (the originals are rather smaller than the digits on yours), but that isn't such a big issue as many were so treated when they went through ordnance. The bracket looks original, as does the scope. Nice find.
ATB.