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.