15 USC 2101 - Marking requirements

(a) Political items 
The manufacture in the United States, or the importation into the United States, for introduction into or distribution in commerce of any imitation political item which is not plainly and permanently marked with the calendar year in which such item was manufactured, is unlawful and is an unfair or deceptive act or practice in commerce under the Federal Trade Commission Act [15 U.S.C. 41 et seq.].
(b) Coins and other numismatic items 
The manufacture in the United States, or the importation into the United States, for introduction into or distribution in commerce of any imitation numismatic item which is not plainly and permanently marked copy, is unlawful and is an unfair or deceptive act or practice in commerce under the Federal Trade Commission Act [15 U.S.C. 41 et seq.].
(c) Rules and regulations 
The Federal Trade Commission shall prescribe rules for determining the manner and form in which items described in subsection (a) or (b) of this section shall be permanently marked.
(d) Exemption 
Subsections (a) and (b), and regulations under subsection (c) of this section, shall not apply to any common carrier or contract carrier or freight forwarder with respect to an imitation political item or imitation numismatic item received, shipped, delivered, or handled by it for shipment in the ordinary course of its business.