cover 1884 (4 Sept.) envelope (front and back split and rejoined, tiny pinholes) with corner card imprint "Legation of the United States. BANGKOK, SIAM." to New York (20.10 arrival), bearing Hong Kong 1883 CA 10c. green (inconsequential creasing at top), cancelled by "BANGKOK" c.d.s. and showing, on reverse, "HONG/KONG/B" c.d.s. (13.9) and "NEW YORK/PO/PAID ALL" duplex (19.10). A great rarity and a major exhibition item. Ex Knox correspondence and unrecorded by Webb. The only known use of the 10c. on cover. B.P.A. Certificate (1987). Photo in colour