Invert error

It is easy for a printing plant worker to insert a half-finished sheet the wrong way around, resulting in the inverts.

The Dag Hammarskjöld invert of 1962 consists only of a misprinted yellow layer, and it is not immediately clear that the white area is not a deliberate element of the design.

In 2013 the U. S. Postal Service offered a six-stamp souvenir sheet commemorating the famous Inverted Jenny issue.

These stamps replicated the famous upside-down airplane image, but did not duplicate the original 24¢ denomination, instead being valued at $2.

To publicize this issue, the Postal Service announced that one hundred sheets bearing six non-inverted Jenny images had also been printed and were being randomly distributed, ensuring that a few fortunate customers who had ordered the normal sheet would instead receive an inverted invert of far greater value.