EXTREMELY FINE USE OF THE 10-CENT 1869 PICTORIAL ON A LETTER TO FRANCE, PREPAID FOR THE 10-CENT DIRECT RATE BUT SENT BY BRITISH OPEN MAIL.
The 1857 U.S.-French postal treaty expired on Dec. 31, 1869, making it difficult to fully prepay postage between the two countries, and impossible to fully prepay postage to France with U.S. stamps alone (with the exception of the unannounced Phantom Rate from New York via British mails). This cover was prepaid for the 10c direct rate to France (with French postage due), but was sent by British Open Mail, which required only 4c.
Ex Caspary -- the $210 realization in the 1956 Caspary sale caused Ashbrook to muse about what factors could have driven up the price to such an extraordinary level (Special Service, page 561, photo 277) and "European Connoisseur"