There is a lot of misinformation being posted by people, so here is the letter of the law as it applies to manufacturers:
Marking Requirements
Serial Number
Must be conspicuously engraved, cast or stamped (impressed) on the firearm frame or receiver
The serial number cannot duplicate the serial number appearing on any other firearm the importer previously imported
For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the serial number must be to a minimum depth of .003 inch and in a print size no smaller than 1/16 inch
Name of Manufacturer
Must be conspicuously engraved, cast or stamped (impressed) on the firearm frame, receiver, barrel or slide
For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the serial number must be to a minimum depth of .003 inch
Country of Origin
Must be conspicuously engraved, cast or stamped (impressed) on the firearm frame, receiver, barrel or slide
For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the country of origin must be to a minimum depth of .003 inch
Model Designation (if assigned)
Must be conspicuously engraved, cast or stamped (impressed) on the firearm frame, receiver, barrel or slide
For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the model designation must be to a minimum depth of .003 inch
Caliber or Guage
Must be conspicuously engraved, cast or stamped (impressed) on the firearm frame, receiver, barrel or slide
For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the caliber or gauge must be to a minimum depth of .003 inch
Marking Requirements
Serial Number
Must be conspicuously engraved, cast or stamped (impressed) on the firearm frame or receiver
The serial number cannot duplicate the serial number appearing on any other firearm the importer previously imported
For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the serial number must be to a minimum depth of .003 inch and in a print size no smaller than 1/16 inch
Name of Manufacturer
Must be conspicuously engraved, cast or stamped (impressed) on the firearm frame, receiver, barrel or slide
For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the serial number must be to a minimum depth of .003 inch
Country of Origin
Must be conspicuously engraved, cast or stamped (impressed) on the firearm frame, receiver, barrel or slide
For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the country of origin must be to a minimum depth of .003 inch
Model Designation (if assigned)
Must be conspicuously engraved, cast or stamped (impressed) on the firearm frame, receiver, barrel or slide
For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the model designation must be to a minimum depth of .003 inch
Caliber or Guage
Must be conspicuously engraved, cast or stamped (impressed) on the firearm frame, receiver, barrel or slide
For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the caliber or gauge must be to a minimum depth of .003 inch