From 1939 to April 1945 Erhard Riedel was head of the Vienna department of the Reichspostmuseum (Reich Postal Museum). He succeeded Emanuel Czezik-Müller, who had been honorary director since 1936 of the Post- und Telegraphenmuseum. He had a doctoral degree in law and had worked for the postal service since 1927. From 1932 (with an interruption in 1933/34) he was a member of the National Socialist Betriebszelle (factory cell) at the post office headquarters. He joined the NSDAP on 1 May 1938 and was classed as an "alter Kämpfer" (old comrade). Apart from working as museum director, he was also a reader during the war at the Hochschule für Welthandel (University of World Trade) and head of the Institute for the History of the Postal Service, part of the University of Vienna from 1943 to 1947. Because of his NSDAP membership, he was dismissed as museum director after the war and failed in his efforts to be reinstated in the postal service. His successor was the chemist August Nitsche. Until his death in 1958, he wrote articles about the history of the postal service.