§ 137.04 DEFACING IDENTIFICATION MARKS OF FIREARMS.
   (A)   Any person who shall knowingly or intentionally change, alter, remove, or obliterate the name of the importer's or manufacturer's serial number of any firearm commits a Class 2 felony.
   (B)   A person who possesses any firearm upon which any such importer's or manufacturer's serial number has been changed, altered, removed, or obliterated commits a Class 3 felony.
(ILCS Ch. 720, Act 5, § 24-5)