§ 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 to be prosecuted under appropriate state law.
   (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 to be prosecuted under appropriate state law.
   (C)   Nothing in this section shall prevent a person from making repairs, replacement of parts, orother changes to a firearm if those repairs, replacement of parts, or changes cause the removal of the name of the maker, model, or other marks of identification other than the serial number on the firearm’s frame or receiver.
   (D)   A prosecution for a violation of this section may be commenced within six years after the commission of the offense.
(ILCS Ch. 720, Act 5, § 24-5) Penalty, see § 130.099