4x6" single-sided postcard has classic image of Superman breaking chains w/"Superman" comic book title logo above. Postcard was issued by New York, NY. radio station WOR 710, which began broadcasting on Feb. 22, 1922. In partnership w/Chicago radio station WGN and Cincinnati radio station WLW, WOR formed the Mutual Broadcasting System in 1934 and became its New York flagship station. Mutual was one of the "Big Four" national radio networks in the US during the 1930s–1980s. This postcard dates to the 1940s as "The Adventures Of Superman" serial came to radio as a syndicated show on WOR on Feb. 12, 1940. On Mutual, it was broadcast from Aug. 31, 1942, to Feb. 4, 1949. Text on card notes that the show does not have a studio audience and as such, WOR cannot provide tickets. This is a Mutual file copy as unused reverse has "File - Mutual" stamp. Minor corner tip bumps but o/w NM. Rare and one of only a few known examples. First we've offered in our 47 years.