'Mona Lisa of the stamp world' that cost just one cent when it was new in 1856 set to sell for millions

To the schoolboy stamp collector who plucked it from a pile of family papers more than a century ago, it was simply a new addition to his collection.

But now a 1-cent postage stamp is set to become the most expensive in the world. The unremarkable-looking 1856 British Guiana 1-cent Magenta is set to sell for an amazing £12million at auction. It is described by experts as the Mona Lisa of the stamp world and hasn't been displayed publicly since 1986. Measuring 1inch by 1 and 1/4 inches, it bears the image of a ship with the former colony's motto, 'We give and expect in return' in Latin. The image is in black on magenta paper. It first belonged to a Scottish boy, Vernon Vaughan, who spotted it at the age of 12 in 1873 when he was living with his parents in the former colony, now known as Guyana. He sold it on for a few shillings to fellow Scot, Neil R McKinnon, to buy more stamps. Each time it changed hands, the stamp increased in value. By 1980, it had reached a then record price of £402,000 -- equivalent to about £1.5million today -- when John E Du Pont bought it. However, Du Pont, heir to the eponymous chemical company fortune, died in prison in 2010 after he was convicted of fatally shooting a 1984 Olympic champion wrestler 13 years earlier. The stamp is now being sold by his estate, which will designate part of the proceeds to the Eurasian Pacific Wildlife Conservation Foundation that du Pont championed during his lifetime. The stamp is being sold at Sotheby's in New York on June 14, where it will easily fetch a world record price if it sells within its estimate. Allen Kane, director of the Smithsonian National Postal Museum, said: 'You're probably not going to find anything rarer than this. It's a stamp the world of collectors has been dying to see for a long time.' David Beech, a curator of stamps at the British Library before he retired last year, said it was like buying the Mona Lisa. David Redden, director of special projects and worldwide chairman of Sotheby's books department, said it was 'the superstar of the stamp world'. He added: 'I have been with Sotheby's all my working life, but before I knew about the world's greatest art, I knew about the British Guiana. As a schoolboy stamp collector, it was a magical object.' The stamp will go on display in London before its sale. The current world auction best for a single stamp is £1.41million in 1996 -- equivalent to £2.24million today -- for the Swedish Treskilling Yellow. When the Treskilling Yellow was sold, it was most expensive item in the world by weight. https://www.youtube.com/watch?v=-17IhjeIttY