The Inverted Jenny was a United States postage stamp first issued on May 10, 1918 in which the image of theCurtiss JN-4 airplane in the center of the design appears 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. A center-line block catalogs for $600,000, which is probably low; a single inverted Jenny was sold at a Robert A. Siegel auction in November 2007 for US $977,500. In December 2007 a mint never hinged example was sold for $825,000. The broker of the sale said the buyer was a Wall Street executive who lost the auction the previous month. A block of four inverted Jennys was sold at a Robert A. Siegel auction in October 2005 for US $2.7 million.
In late October 2005 the unique plate number block of four stamps was purchased by a then anonymous buyer for $2,970,000. The purchaser was revealed to be U.S. financierBill Gross. Shortly after purchasing the Inverted Jennys he proceeded to trade them with Donald Sundman, president of the Mystic Stamp Company, a stamp dealer, for one of only two known examples of the USA 1c Z Grill. By completing this trade, Gross became the owner of the only complete collection of U.S. 19th century stamps.
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