Personally I think provenance is anything reasonable, particularly if you have to actually ask for it from the seller. If I buy a normal badge and, after asking the seller after the auction, I get a reasonable answer (a non-descript NCO in a regular unit), I'm fully satisfied. 5 times out of 10 they simply say they don't know. However, I would never buy an item
because of a claimed provenance, and appreciate that the same not true for high-end badges (i.e. SF bits).
Take this for instance:
It's certainly real, and quite interesting - a souvenir from the Colombian battalion in Korea. The seller told me, privately, that it belonged to his father (a member of the Middlesex Rgt) who served in Korea - and probably swapped it or bought it there. Since General MacArthur, paratroopers or the 101st airborne are not involved, I'm perfectly satisfied with that as provenance which I make a note of.
American collectors tend, in my experience, to be more concerned with an item having "recorded" history. That said, unless you are lucky as Rob says and get it directly from a veteran, we'd all just have to accept that 99% of any badges will never have any kind of history to them. That, in my belief, is a bit of a shame.