Frederick C. Davis
According to the Science Fiction Encyclopedia: "US author of pulp fiction, sometimes under pseudonyms, from 1922 or earlier. He published detective fiction in book form from the mid-1930s until the end of his active career in the late 1960s."
"Under the House Name Curtis Steele, Davis was responsible for the lead novels in the magazine Operator #5 from April 1934 to November 1935. Thirteen of these appeared in book form in three separate paperback series, the first beginning with Legions of the Death Master (1966), the second with The Masked Invasion (April 1934 Operator #5; 1974), and the third with Cavern of the Damned (1980)."