Ask 10 different ATF agents the same question and you will receive 10 different answers!
I think that all the requirements as to marking the gun are imposed upon the importer. Once the consumer purchases the gun, they are free to obliterate any markings on the gun EXCEPT for the serial number. There is no law or regulation that I am aware of that forbids removal of any markings other than the serial number. The import markings are basically there to track the firearm from the importer to the FFL holder. Once it is out of the control of the FFL holder, the buyer can remove the markings. If it were illegal to remove the markings, then it is illegal to change out the bbl of a gun that has the importers mark on the bbl, as this would constitute "removing the importers mark"!!!!
If a law enforcement agency is trying to track a gun they will be using the serial number, not who the importer was. Besides, if it is a Luger, who's going to know if an importers stamp was originally there or not?
