The Inverted Jenny

The inverted Jenny (or Jenny Invert) is a United States postage stamp of 1918 in which the image of the Curtiss JN-4 airplane in the center of the design was accidentally printed upside-down; it is probably the most famous error in American philately. Only 100 of the inverts were ever found, making this error one of the most prized in all philately;

A block of four inverted Jennys was also sold at a Robert A. Siegel auction in October 2005 for US$2.7m. And in November 2007 an inverted Jenny was sold for US$977,500. In December of 2007, a mint, never hinged example, meaning one not previously affixed to a stamp album, was sold to an unidentified Wall Street executive for $825,000.