Firstly congrats to the OP on a very rare button. Shame the backmarks not there to inform us with more details.
I like CBG explanation on how post war buttons may have found there way into old CW camps/sites. It interests me because so many assume provenance is about where something is found, & its not, its more than that its firstly about a factual ID, then it builds a picture. This one though still seems pretty grey without an exact ID, & sounds like it could just cross that line into CW.
All good stuff.