Today’s the day. The is set to fly again! If you’re in the Washington, D.C., area and are interested in attending the official release ceremony, come join us at the Smithsonian’s National Postal Museum, just steps from Union Station. The event kicks off at 1 p.m. and coincides with the grand opening of the museum’s new William H. Gross Stamp Gallery.

This stamp features a new version of perhaps the most famous error in the history of U.S. stamps: the Inverted Jenny, a 1918 misprint that mistakenly showed a biplane flying wrong side up. Reprinted with a $2 denomination to make them easily distinguishable from the 24-cent originals, the Inverted Jennys on this sheet commemorate the many ways a single stamp can turn a moment in history upside down.

For nearly a century, philatelists have chased the Inverted Jennys, accounting for nearly all 100 of them even as the stamp became one of the country’s best known philatelic treasures. In a 1993 episode of The Simpsons, Homer Simpson discovers (and, humorously, discards) a highly unlikely sheet of 40 Inverted Jennys, and the stamp made headlines beyond philatelic circles in 2006, when a faked version appeared on an envelope for an absentee ballot in Broward County, Florida.

Today, two Inverted Jennys soar among the Postal Museum’s treasures. The Inverted Jenny is said to be the postage stamp most often requested for viewing by visitors, and a third Inverted Jenny on long-term loan from the New York Public Library’s Benjamin K. Miller Collection was a major attraction in the Postal Museum’s “Rarity Revealed” exhibition from 2007 to 2009.

Come on down to the museum and check them out!