The following tutorial will show you around the part 479 landing page.
27 CFR Part 447
Importation of Arms, Ammunition and Implements of War
27 CFR Part 478
Commerce in Firearms and Ammunition
27 CFR Part 479
Machine Guns, Destructive Devices, and Certain Other Firearms
27 CFR Part 555
Commerce in Explosives
27 CFR Part 646
Contraband Cigarettes
27 CFR Part 771
Rules of Practice in Explosive License and Permit Proceedings
Effective date is the date this part was last amended
The person affixing to a Form 1 (Firearms) a “National Firearms Act” stamp shall cancel it by writing or stamping thereon, in ink, his initials, and the day, month and year, in such manner as to render it unfit for reuse. The cancellation shall not so deface the stamp as to prevent its denomination and genuineness from being readily determined.