1854, 1857 San Francisco, Ca. to Great Britain, two folded covers, 1854 (Mar. 28) carried by Oregon from San Francisco Apr. 1st to Panama Apr. 15th, then by Illinois Chagres Apr. 17th to New York Apr. 29th, then by Collins Line Arctic to Liverpool arriving May 10th, green Liverpool 'America' (5.10) backstamp and matching green "ART-5 / U.S. Pkt." two-line handstamp, black "1/1½" due rating handstamp, red Worcester (5.12) arrival backstamp; 1857 (Nov.) from San Francisco via Panama and N.Y., then by Cunard Line Niagara from Boston Dec. 2nd to Liverpool arriving Dec. 14th, black Liverpool 'America' (12.14.57) backstamp and "ART-5 / Br. Pkt." two-line, matching "1/2½" due rating, handstamp, couple tape stains, F.-V.F., A scarce pair of San Francisco covers showing the two Article 5 markings. Estimate  $400 - 600. The U.S. - G.B. Treaty specified the rate under Article 5 of the treaty and handstamps were applied at Liverpool stating "ART-5 / B.R. PKT." and "ART-5 / U.S. PKT.". $0 (Image)