Amazing facts about the British Guiana One-Cent Magenta, which was created in 1856 and is the most famous and valuable stamp in the world. “It is the Mona Lisa of philately,” said David Beech, a philatelic expert. “It is the one stamp that every philatelist and every collector would have heard about and seen an illustration of". The stamp, the only one of its kind, has gone on display at Sotheby’s London headquarters before its sale in New York and will be on public view this week. Beech, formerly the curator of the British Library philatelic collections, said its fame was enhanced by the people who had owned it – and those who desperately wanted to own it.