British Guiana 1c magenta

Short of stamps while waiting for a shipment from London, British Guiana's postmaster had the colony's newspaper print an emergency supply in 1856. One 1 cent magenta survives. A Scottish boy, Vernon Vaughan, found it among his family's letters in 1873 and sold it to a local collector for 6 shillings. From there it passed through the greatest collections: Philipp von Ferrary, Arthur Hind and finally John E. du Pont. It sold at Sotheby's in New York for $9.5 million in 2014, and again there in 2021 for $8.3 million to the dealer Stanley Gibbons. Crude to look at and unmatched in story, it is the world's most famous unique stamp.