(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)