375rd Heinrich Köhler auction - Day 1

BRITISH POST OFFICE: "C51" on 4 d. vermilion, pl. 10 with adjacent red "ST. THOMAS PAID MY 18 69" on lettersheet from Mayaguez, Puerto Rico to Philadelphia, endorsed "p.W.I.Str.", changed in "Str. via New York", additionally franked with US 1861/67, 10 c. green with cork cancel and adjacent "N.YORK STEAM SHIP JUN 4". The letter was privately carried to St. Thomas to forwarding agent George A. Flips & Co. (blue oval handstamp on reverse), intended to be carried by the Brazilian line S.S. Mississippi, due at St. Thomas on May 14 and therefore franked with the US stamp. However, the steamer wrecked at Martinique and the forwarding agent added the British stamp to catch the British packet departing on May 18 for Havana. A very fine and rare letter, just 3 similar covers recorded