I would add the following to Chris's excellent comments:
From Siegel:
Quote:
Approximately 180 used examples have been certified by The Philatelic Foundation, of which only one-quarter are sound. The cancel most often seen on genuine used examples of the 90c is the New York red grid.
The six recorded 90c 1860 covers:
1) Sep. 11, 1860, to Augustine Heard & Co., Shanghai, single franking for double rate, ex Gibson, Hindes and Kapiloff
2) Nov. 3, 1860, to Barcelona, Spain, ex Caspary, Rust and Kapiloff
3) Nov. 9, 1860, to Augustine Heard & Co., Shanghai, ex Needham, Paliafito, Ishikawa, Myers
4) Jan. 8, 1861, single used on legal-size cover from Cincinnati, ex Filstrup, Grunin
5) Jul. 16, 1861, to Edwin Howland, Cape of Good Hope, used with 1c pair, 3c, 10c and 30c for four-times 33c rate, ex Jacobs, Newbury, Ishikawa
6) Jan. 26, 1861, to Mackellop Stewart & Co., Calcutta, India, used with 12c and 30c