Amazing Stories, Vol. 30, No. 3 (March 1956). Digest size. Cover art by Edward Valigursky for “The Iron Virgin” by C. H. Thames.

From Wikipedia

Amazing Stories is an American science fiction magazine launched in April 1926 by Hugo Gernsback’s Experimenter Publishing. It was the first magazine devoted solely to science fiction. Science fiction stories had made regular appearances in other magazines, including some published by Gernsback, but Amazing helped define and launch a new genre of pulp fiction.