Sub contractor receiver question

I know a couple of manufacturers used subcontractors to make receivers for them. My question is was it common to see such receivers with ground out serial numbers and restamped numbers on them? Is this something that's less desirable or something that's not right?

Bad like a screw up on the subs part or bad like something is fishy with a ground serial?

Underwood receiver,   Underwood marked with serial number with a plain W underneath. Not mine, but in picture you can see serial was grounded then restamped most likely by hand.

Hmm, does the heal have the Underwood flaming bomb?

OK, look real closely next to the W is there any signs of a letter on either or both sides?

I'm not aware of any signs of grinding on a carbine that is a good thing. Some say never say never and can't speak for others, but at the first sign of metal grinding, welding, etc....time to move on.

The only pic isn't clear and when I try to cut it smaller to fit here it just comes up as a blur. Basically what's there is a ground out serial with a hand stamped one over the ground One. Like stated above I am going to move on, just not worth it. I thought maybe something like this may of been seen all the time with sub made receivers but that's not the case.   Thanks to all for responding 👍