In 1944, the British created this propaganda forgery depicting Field Marshal Erwin von Witzleben, a senior plotter of the July 20, 1944, assassination attempt on Hitler.
The stamp design is an imitation of the German MiNr. 863, released in 1943 to commemorate the 20th anniversary of the Beer Hall Putsch.
The revised text reads “Gehangt am 8 Aug 1944” (Hanged on 8 August 1944).
For more on this issue, see Propaganda and Espionage Philately, by SGM Herbert A. Friedman (Ret.).