In 1918, the US Postal Service began airmail service and since it would cost more than the regular first class 3 cents postage, they issued a 24 cent airmail stamp. The stamp showed a picture of the airplane that was going to carry airmail letters – a remodeled Curtiss Jenny JN-4HM. Since the stamp was printed in red and blue, in those days it had to be sent through the printing press twice – once for each color – and while they always tried to be careful when inserting the sheets for the second run, one incorrectly (inverted) sheet wasn’t noticed and was released. Eventually the sheet was broken into single stamps and sold to collectors at in 2016, at the New York Stamp Expo, one “Inverted Jenny” stamp was sold at auction for $1,175,000. That was the first US Postal Service inverted misprint.