The on-sale date is from the publication date recorded in the Catalog of Copyright Entries, Part 2, Periodicals, 1940, New Series, Vol. 35, No. 4.
title from cover
Battefield is credited with pencils and inks in the Devil's Dagger story in this issue, and that art is similar to this story. The faces of the villains are exact matches, long chin, small eyes and long noses. Also notice the face in sideview in the Battefield scan on Jerry Bails' Who's Who from Target comics with pencils by Battefield, and from the same period.