The critical thing is to have a factory letter, stating how the gun was shipped, in
terms of the finish. Presumably, there will be a stamp on the grip frame, of
something like 6.50, meaning a return to the service department in June (6) of 1950.
There might also be marks like <S>, or <G>, or a P with a circle, or perhaps some other
marks, on the grip straps, and possibly on the flat under-side of the barrel.

Mike Priwer