A scrap of dark-red paper faintly printed in black, the only surviving example of a legendary stamp that sold for one cent in 1856, is expected to fetch US$20 million at auction, reinforcing its reputation as the world's most famous and valuable stamp.
The British Guiana one-cent magenta was most recently owned by an American millionaire who died four years ago in a jail cell.
If the stamp reaches the predicted price at a Sotheby's sale in New York on June 17, it will set a new record for a single stamp.
The stamp was one of an emergency printing of several denominations by the local Official Gazette newspaper in British Guiana in 1856, when storms delayed a shipment from the UK and the postmaster was in danger of running out of stamps. Apart from the schoolboy who first recognised its rarity, it has brought no luck to a succession of eccentric private owners.
The last owner, John du Pont, an heir to the DuPont chemical fortune, paid nearly US$1million for it in New York in 1980. The last time the stamp was seen in public was 1986.
Ten years later, suffering from severe mental illness, du Pont shot dead the Olympic gold-medal wrestler Dave Schultz - after many years of sponsoring and helping in the training of Schultz and other US Olympic wrestlers. His illness meant he escaped the death penalty but he was found dead in his Pennsylvania prison cell in 2010, aged 72.
The stamp is now being sold by his estate, with some of the money going to another of the causes he championed, the Eurasian Pacific Wildlife Conservation Foundation.
The stamp's first collector, who sold it to a dealer for a few shillings in 1873, was Vernon Vaughan, a 12-year-old Scottish schoolboy living with his family in British Guiana, who found it among his uncle's papers. In the 1880s it was bought by Count Philippe la Renotiere von Ferrary, one of the wealthiest men in Europe. He intended to leave his collection to Berlin's postal museum but the French state seized it as part of post-war reparations, and sold the British Guiana in 1922, when it set its first world record: the American collector Arthur Hind outbid several rivals, including the stamp-obsessed King George V, and paid £7,343 (HK$95,000). According to stamp-collecting legend, a second copy did turn up soon afterwards, which Hind bought. He then set it on fire, saying: "I still possess the only copy."
David Redden, Sotheby's chairman and a books specialist, said he was overawed to have the stamp in his care.
"I have been with Sotheby's all my working life, but before I knew about the world's greatest works of art, before I knew about the Mona Lisa or Chartres Cathedral, I knew about the British Guiana," he said.
"For me, as a schoolboy stamp collector, it was a magical object, the very definition of rarity and value, unobtainable rarity and extraordinary value. That schoolboy of long ago would be bemused and astonished to think that he would one day, years later, be temporary guardian of such a world treasure."