This formal ATF ruling Clarifies certain gunsmith activities for Dealers, Manufacturers such as bluing, anodizing, powder-coating, plating, polishing, heat and chemical treating that have caused confusion over activities requiring a federal firearms manufacturers license, firearms marking requirements, and firearms record keeping requirements.
ATF Issues Manufacturing Ruling
http://www.atf.gov/press/releases/2010/12/122910-atf-issues-manufacturing-ruling-atf-2010-10.html
ATF Rul. 2010-10 – Manufacturing Operations May Be Performed by Licensed Gunsmiths Under Certain Conditions
http://www.atf.gov/regulations-rulings/rulings/atf-rulings/atf-ruling-2010-10.htm
ATF Issues Manufacturing Ruling
http://www.atf.gov/press/releases/2010/12/122910-atf-issues-manufacturing-ruling-atf-2010-10.html
ATF Rul. 2010-10 – Manufacturing Operations May Be Performed by Licensed Gunsmiths Under Certain Conditions
http://www.atf.gov/regulations-rulings/rulings/atf-rulings/atf-ruling-2010-10.htm