Inverted Jenny Stamp
The Inverted Jenny Stamp was a 24 cent stand released by the USPS in 1918. It has an image of a Curtiss JN-4 Airplane on it, also known as a “Jenny”. However there was a pane of these stamps that had a misprint. That being that the plane was printed upside down. Those stamps are so incredibly rare they can end up going for a lot. In 2018, one of them went for $1.593 million.