To amateurs, the 1856 British Guiana One-Cent Magenta stamp that measures a mere 2.5 cm by 3.2 cm may appear to be like any other ancient postage stamp. However, for philatelists this octagonal scrap of paper that bears an illustration of a three-masted ship is a one-of-a-kind treasure, for which an avid collector recently paid $9.5 million. According to Sotheby's, the One-Cent Magenta is not just the world's most expensive stamp sold at an auction but also its most valuable object by weight and size!