1849 (May 8) Boston, Mass. to Warrington, England, folded letter carried by Cunard Line Cambria from Boston May 9 to Liverpool arriving May 21, Liverpool "America 22MY 1849" cds on flap and matching "d9½" rate handstamp, blue Warrington (5.22) arrival backstamp, Very Fine, one of only two recorded examples where handstamp used on loose letter placed on board British steamer in U.S. port without entering American postal system. The treaty had no provision for such a use. Estimate  $200 - 300. Special "d9½" rate handstamp despatched to Liverpool from London on March 19, 1849 to be used on mail paid to New York from California (not yet a state) and unpaid from New York. Remaining postage due was 8d transatlantic postage plus 1½d British postage under new treaty. $0 (Image)