Post Office of Ghent (French: Gand) on 13 August 1920. When the discovery was made, only 7 copies remained. At the moment there are 17 known copies: 15 unused and 2 used. The only known cancellation is "Gand 13 August 1920". In 1942 a stamp dealer from Brussels, who had two copies of the stamp, was murdered. The murderer and the two stamps were never found. Value The cancelled stamp is valued at €75,000 and is one of the most expensive Belgian stamps. Popular culture In 2003 the stamp was the subject of the comic book Het mysterie van de omgekeerde zegel (The mystery of the inverted stamp) in the series Stam en Pilou. In 2004, the stamp was the subject of a children's book De Omgekeerde Dendermonde (The Inverted Dendermonde) by author Henri Van Daele. In Season 32, episode 11 of The Simpsons, The Dad-Feelings Limited, Marge threatens to lick Postage Stamp Fellow's Inverted Dendermonde to force him to reconnect with his son, Comic Book Guy. References and sources Officiële Belgische Postzegelcatalogus 2010. Scott 2007 Standard Postage Stamp Catalogue, Volume 1 Postage stamps Postage stamps of Belgium Postage stamp invert errors 1920 works 1920 in Belgium