The "Inverted Jenny" (C-3a) is a 24-cent 1918 US Air Mail postage stamp printing error in which the blue central vignette of US Army Curtiss JN-4HM #38262, the nation's first mailplane, appeared as "inverted" on a single sheet of 100 stamps owing to an inadvertent error made by the operator of a hand-rolled spider press by printing the blue vignette impressions upside down after the red frames had previously been printed on the sheet.The 1918 24¢ Inverted “Jenny” (Siegel Auction catalogue, Sale 1010A, June 18, 2011), p. 8 As the Jenny vignette was only inverted on one sheet, this stamp represents the rarest and most valuable known USPOD printing error of all time. A single example (sheet position 57) sold at auction in 2007 for $977,500.00."Robert A. Siegel Auction #946a." SiegelAuctions.com. The stamp was reissued for a limited time as a $2 stamp in October 2013.
