'Holy Grail' of stamps to fetch $20 MILLION at auction - despite costing just one CENT when it was issued in 1856

Frequently described as 'the most valuable stamp in the world', the British Guiana 1c Magenta, pictured, will be auctioned in New York on 17 June. It is the only surviving example of the 'emergency' stamps range launched by the colony's postmaster in 1856, and was discovered by a schoolboy in Demerara in 1873
 http://www.dailymail.co.uk/sciencetech/article-2620558/Holy-Grail-stamps-fetch-20-MILLION-auction-despite-costing-just-one-CENT-issued-1856.html#ixzz30rZesKk1