Yes, in fact, I believe what everyone casually calls the "final acceptance mark" or "master armorer's cartouche" or whatever, is not actually an "inspection" mark at all - but rather simply denotes acceptance into stores.

OM22 is quite clear - for the trapdoor - that, after firing five rounds to test the functioning (not any sort of proof overload - that had already been done) the rear sight was installed, and a (P) was stamped behind the guard - THAT being the final "inspection" mark.