Few questions on IBM s/n 3882XXX

Friend of mine just acquired a IBM carbine s/n 38828XX and it seems partly correct, but there is something regarding the stock and andgd that has us perplexed??
Both the stock and the handgd have the entire serial number stamped inside. Looks very correct and original but we never heard of such a thing.
There is also a small aluminum hand made tag with the last few digits of the s/n that is tacked under the grip. Also the same few digits are stamped a few places on other parts, the slide, the trigger gd group and others.
I suspect these numbers were later added but why and by whom.
Any help is appreciated??
Thanks

What you have is an import. If the serial number is in front of the sling well or just about it then it is a good possibility it came from Israel. If it's inside the sling well then it could have come from almost anywhere. If it's in excellent condition then from somewhere like Norway maybe. Somewhere care was taken with the rifle and not like one of the central American countries. The plate on the bottom of the grip had become a rack type number to ID a certain carbine. Maybe some solders favorite. Serial numbers were never stamped into the wood within the US systems.

purty much what I had suspected. Thanks for the input

Tuna, I prefer to differentiate imports from returns. Imports usually imply a civilian entity involvement whereas a return is a transfer from a foreign government back to ours. Returns have usually remained under some sort of government oversight. Agree?

Yes it very well could be a CMP Bavarian return and if so it will not be marked. BUT it also could be an import too as many of these were sold and brought back to the US. Why I did not notice that it was also stamped with numbers on the different parts, I may have been rushed when I first answered the question but anyway It sure sounds like a Bavarian carbine. If an import it should be stamped on the barrel or the receiver. Century in Vermont imported a lot of these.