I have a rifle that I would like to have a scope mount installed on. Unfortunately, the area on the receiver that would need to be drilled, is the exact spot where the factory serial number is engraved. For reference purposes, it is a surplus Spanish Mauser. (so little collector value to destroy) The SN is on the left side 'bridge,' directly behind the 'large ring,' and the mount is a reproduction side-mount.
There is plenty of space all over the rest of the receiver, where I could have a duplicate SN engraved. What are the rules for 'moving' the SN? I would imagine (of course) that the second one would have to be engraved before the first one can be defaced. Is there any other regulation that covers this? Does the ATF need to be notified, and/or give permission?