While the red and blue 24¢ "Jenny" is famous for being the world’s first airmail stamp, one sheet of these stamps has become the most recognized and famous rarities in the world. Through an error during the printing process, a single sheet of these has an inverted image of the Curtiss Jenny airplane.

     The "Inverted Jenny" sheet was bought on May 14, 1918 at a regular post office by avid stamp collector William Roby for $24. The error was not immediately noticed by the postal clerk because he later commented that he had never seen an airplane before, and therefore did not realize it was upside down.

     However, as a collector Roby immediately recognized the value of such a rare error and sold the entire mint sheet to Eugene Klein a few days later, for $15,000. Before Klein broke up the sheet of 100 inverts, he penciled a position number on the back side of each stamp. This allows each stamp to be precisely located and identified. Of the original 100 stamps, seven 24¢ "Inverted Jennys" have been lost or destroyed since the sheet was broken up, and others have sadly been damaged in some way.

     The wife of millionaire collector Edward Green accidentally used a Jenny invert to mail her husband a letter, producing the only known used "Inverted Jenny". Other stamps have been similarly mistreated, including one man whose maid vacuumed up the rare 24¢ invert inadvertently. After hours of frantic searching, the collector eventually recovered it from the inside of the vacuum. Recently, a single "Inverted Jenny" in excellent condition sold at auction for $977,500. While there are rarer and harder to find stamps on the market, the "Inverted Jenny" remains the most famous and recognizable stamp error in the world.