In the case of the SMLE, in some cases you can determine the history of the arm if you post marking or serial numbers.

For example some lots of SMLE rifles were imported by century from Ireland circa 1985 and can be identified by the serial numbers.

Century imported a number of Portuguese SMLE rifles in the pre 1968 period. These rifles lack the UKicon export proofs of the period, but can only be identified if you have the time of import, as there were other rifles imported from Denmarkicon (early 1960s), Spain (1959) that were not UK export marked.

SA police SMLE and BSAP rifles can be identified by the markings on the wood.

Same is true of NZ SMLE rifles.

Australianicon issue rifles can often be traced by their markings and if they have century markings, most likely they came out of Pakistan, the big Joe Jovino import lot not being so marked.

If they have the ID disc missing, they generally have WWII overseas issue history, as the ID discs were removed and often the whole not filled. Such guns should also have a lot of history and should have UK export marks and commercial proofs.

all comes down to the details.