I received my M1 Carbine from the CMP a couple of weeks ago, and I noted then that the serial number on the Certificate of Authenticity didn’t seem right to me. According to the information I could find, the serial number the CMP thought the rifle carried would have made the receiver a Saginaw, but it (and the barrel) were clearly marked “IBM CORP.” So I fired off an email noting that I thought they’d misread the second digit of the S/N as a “6” rather than an “8”, where the “8” would have made it a 1943 production IBM unit.
I just received a new receipt and a new Certificate of Authenticity in the mail with the correct serial number. That’s pretty good service!