for me if it's not an american gun and does not have an importer mark then I assume it was a bring back... I prefer those anyway, my savage no4 MK1* has the CAI etchings in it and I cringe every time I see it.
Import marking did not start until the NFA in 1968. If your foreign made fire arm does not have import marks it's a pre 1968 import. Lot of fire arms got imported between 1948 and 1968. One exception is CMP, they are exempt from import marking the rifles they import.