The Dag Hammarskjöld invert is a 4 cent value postage stamp error issued on 23 October 1962 by the United States Postal Service (then known as the Post Office Department) one year after the death of Dag Hammarskjöld, Secretary-General of the United Nations, in an airplane crash.
The Dag Hammarskjöld error stamp was created as a tribute to Dag Hammarskjöld, the former Secretary-General of the United Nations, who tragically passed away in a plane crash.