Cal. Penal Code § 23910

The Department of Justice, upon request, may assign a distinguishing number or mark of identification to any firearm whenever the firearm lacks a manufacturer’s number or other mark of identification. Whenever the manufacturer’s number or other mark of identification or a distinguishing number or mark assigned by the department has been destroyed or obliterated, the Department of Justice, upon request, may assign a distinguishing number or mark of identification to any firearm in accordance with Section 29182.