BPC § 22179

The variation between the actual fineness of the gold or its alloy contained in any article and that indicated by the quality mark applied to such article shall not exceed the tolerances for fineness prescribed for articles made of gold and its alloys which are to be moved in interstate commerce by that act of the United States Government entitled “An act forbidding the importation, exportation or carriage in interstate commerce of falsely or spuriously stamped articles of merchandise made of gold or silver or their alloys, or for other purposes,” approved June 13, 1906 (34 Stats. 260; 15 U.S.C. Secs. 294-300, inclusive).