single tied by blue "Pony Express San Francisco Jun 1" Running Pony handstamp to 10c Green Star die entire (U32), entered the mails with green "St. Joseph Mo. Jun 13" datestamp, addressed to New York City, red and blue flag and cannon patriotic design with "The Union must and shall be preserved" imprint, Hutchings & Rosenfield printers, extremely fine, one of just three recorded Pony Express patriotic envelopes, one of which is the famed cover to Germany, a sister cover to the one offered here (dated June 12) is in the permanent collection of the National Postal Museum, one of the most extraordinary and beautiful pieces of postal history in existence, 2022 Philatelic Foundation certificate, Frajola-Walske-Kramer census #E89