Welcome to the forum. While restoration is an expensive potential option, finding a replacement frame may be the way to go - but - realize that in either the case you keep the original frame or replace it it won't become collectible.
It may be possible to guess on when the frame was replaced if we can get a look, but it's likely it was an armory replacement either during the war, or as part of a Russian Capture / East German rework effort.
Most others would not bother to "X" out things.
If it's mechanically functional, I'd leave it as is. These are hand fit firearms, and it will take some work to properly fit a replacement frame, side plate, firing pin etc...
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 Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.
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