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. 4.
Last appearance, even though the last panel states he will return in a future issue of Blue Beetle.
The last half page of the story is an illustrated promo for a new hero to appear in the pages of Fantastic Comics: The Gladiator.
Bill Black states that Jerry Bails' "Collector's Guide: The First Heroic Age" from 1969 and Howard Keltner's "Index to Golden Age Comics Books" from 1976 both list the feature.
Bails' Who's Who does not list the feature nor Harry Graves.