[ithacaartist]

I don't think it takes all that big a hammer...

The "any part that fits" may not be that far off, Fresh parts in many circumstances, but sometimes the new numbers have been impressed right over the old. Another technique would be to work away enough material to remove the old markings before applying fresh ones.

If my understanding is correct, it was done during a couple of processes. One would be an official or semi-official way, most likely with the fresh parts you imagined, at a weapons depot, or maybe even at a military unit level, by armorers. The DDR did this post WWII to plenty of guns, rather crudely in some instances-- but not all, some were left original and untouched. Another reason is for a scammer to create an all matching gun, to deceive and reap a high price. Not so much a worry in the shooter price range, but for rare/valuable guns it is an art. The forgers slip up, their techniques exposed and identified, and they learn to better, more subtle work by knowing thereafter what not to do.