The "Inverted Jenny," 1918, one of the rarest and most valuable stamps in the world, celebrates the first air mail in the U.S.—by depicting an inadvertently upside ... new 24-cent stamps with ...

To a layman, the Inverted Jenny is just a 24-cent ... more airmail stamps had come in. "He brought forth a full sheet," Robey said, "and my heart stood still." The image was upside down!