(a) A person commits the offense of possession of a defaced firearm if he or she knowingly possesses a firearm with a manufacturer's serial number or other identification mark required by law that has been removed, defaced, marred, altered, or destroyed.
(b) It is a defense to a prosecution under this section that:
(1) The person reported the possession to the police or other governmental agency prior to arrest or the issuance of an arrest warrant or summons; or
(2) The firearm was manufactured prior to January 1, 1968.
(c)
(1) Possession of a defaced firearm is a Class D felony.
(2) However, possession of a defaced firearm is a Class A misdemeanor if the manufacturer's serial number or other identification mark required by law is merely covered or obstructed, but still retrievable.