48 C.F.R. § 225.903

(b)(i) For an explanation of the term “supplies,” see PGI 225.903(b)(i).

(ii) The duty-free certificate shall be printed, stamped, or typed on the face of, or attached to, Customs Form 7501. A duly designated officer or civilian official of the appropriate department or agency shall execute the certificate in the format provided at PGI 225.903(b)(ii).