15¢ Black, E. Grill (91), horizontal pair, used with 12¢ Black, F. Grill (97), tied by segmented cork cancel and "Fairhaven Ct. May 17" (1869) duplex circular datestamp on cover to Hong Kong, China, from the Collins correspondence, sender's "Via Marseilles" route directive, blurry strike of red "New York Paid All Br. Transit May 18" backstamp, "32" credit handstamp struck three times (over "26" credit applied in error), red "London Paid" transit datestamp (May 28) and "1d" British Colonial credit handstamp which ties left 15¢ stamp, "Hong-Kong Marine Sorter, Singapore to Hong Kong, JY ?/15 69" Marine Sorter backstamp, Very Fine cover with an extremely rare use of the 15¢ Lincoln for the 42¢ rate to China by British Mail via Marseilles, especially desirable with the Hong Kong Marine Sorter backstamp which was introduced in 1868 to expedite mails by having an official clerk sort letters on board the steamer from Singapore to Hong Kong
VERY FINE. AN OUTSTANDING 15-CENT LINCOLN COVER WITH A RARE, IF NOT UNIQUE, GRILLED ISSUE FRANKING FOR THE DOUBLE BRITISH MAIL RATE TO SPAIN.
According to U.S.-Spain Mails via British Convention, 1849-1876 by Richard F. Winter (supplement to Chronicle 147, pp. 15-16), the Convention rates effective from Jan. 1, 1868, to Dec. 31, 1870, followed a progression of 10c U.S. per -1/2 oz. and 12c credit to G.B. per 7.5 grams (-1/4 oz.). This letter must have weighed about a half-ounce and was rated as prepaid in New York with a 24c double U.S. credit to G.B. However, the G.B. credit to Spain was 6p, corresponding to the triple 7.5 gram weight class.
With 1985 P.F. certificate