The on-sale date is from the publication date recorded in the Catalog of Copyright Entries, Part 2, Periodicals, 1941, New Series, Vol. 36, No. 1.
Originally credited to Irv Novick, but the movement of the figures are too stiff and clumsy, and none of his faces are found here.
Originally credited to Bernard Klein, but there are none of his faces with angry eyebrows and squinting eyes, nor the angular jaws. The art must be by Hubbell, and matches very well his signed Kardak story in #15. He is credited on this feature by Jerry Bails' Who's Who, and made four stories #12-15.