The Inverted Jenny is a United States postage stamp first issued on May 10 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 one pane of 100 of the invert stamps was ever found, making this error one of the most prized in all philately; an inverted Jenny was sold at auction in November 2007 for US $977,500. In December 2007 a mint, never hinged example (one not previously affixed to a stamp album), was sold for $825,000. A block of four inverted Jennys was sold at auction in October 2005 for US$2.7 million.