1918

The famous “inverted Jenny” stamps - misprinted upside-down biplane - are printed in 1918.

The Inverted Jenny bears the most famous error ever made in an American stamp. There are 100 stamps printed of the upside-down Curtiss JN-4 airplane. The stamp was to honor the nation’s first air mail carrier.

In 2016, one sold for $1,175,000.