The sole-surviving example of a one-cent magenta from British colonial Guyana, the world's most famous postage stamp, is going under the hammer in New York for $10 to $20 million.
Sotheby's has valued the stamp, which was made under British rule in 1856 when a shipment of stamps from England was delayed, and will sell it on June 17.
The "British Guiana One Cent Magenta" has broken a new record for the price of a single stamp the previous three times it was sold at auction since 1922 and has an incredible history.
Bought most recently by convicted murderer and American multi-millionaire, John du Pont, it has not been seen in public since going on display at a stamp exhibition in Chicago in 1986.
David Redden, director of special projects and chairman of Sotheby's books, said the stamp "was a magical object" and the definition of "unobtainable rarity and extraordinary value."
In the mid-19th century the post service in Guyana depended on supplies of stamps being shipped from England.
But when a consignment was delayed in 1856, the postmaster commissioned a contingency supply made locally by printers of the Royal Gazette newspaper.
The printers ran off one-cent and four-cent magentas, and a four-cent blue. The British Guiana is the sole-surviving example of the one-cent magenta.
It was rediscovered in 1873 by L. Vernon Vaughan, a 12-year-old Scottish boy living with his family in British Guyana.
A budding collector, Vaughan found the stamp among a group of family papers and added it to his album.
He later sold it to another collector for several shillings and the stamp eventually made its way to Britain in 1878.
It was then bought by French Count Philippe la Renotiere von Ferrary, perhaps the greatest stamp collector in history, and later donated to a museum in Berlin.
After World War I, France seized his collection as part of war reparations due from Germany and sold the stamp in 1922 at auction to Arthur Hind, a textile magnate from New York.
Hind paid a then record $35,000 for the stamp. It sold for a second record of $280,000 in 1970 and was bought in 1980 by the late du Pont for a third record of $935,000.
It is being sold by his estate. The stamp will go on display at Sotheby's in London, Hong Kong and New York before the auction.
Current day Guyana, which won independence from Britain in 1966, is a small but poor nation of about 700,000 people.