Conn. Gen. Stat. § 29-36: Alteration of firearm identification mark, serial number or name.

(a) No person shall remove, deface, alter or obliterate the name of any maker or model or any maker's number, unique serial number or other mark of identification on any firearm as defined in section 53a-3. The possession of any firearm upon which any identifying mark, number or name has been removed, defaced, altered or obliterated shall be prima facie evidence that the person owning or in possession of such firearm has removed, defaced, altered or obliterated the same.

(b) Any person who violates any provision of this section shall be guilty of a class C felony for which two years of the sentence imposed may not be suspended or reduced by the court, and five thousand dollars of the fine imposed may not be remitted or reduced by the court unless the court states on the record its reasons for remitting or reducing such fine, and any firearm found in the possession of any person in violation of said provision shall be forfeited.