The on-sale date is from the publication date recorded in the Catalog of Copyright Entries, Part 2, Periodicals, 1942, New Series, Vol. 37, No. 2.
Sequence information from Wilson C Souza (July 17, 2010).
Otto Binder says that this was his first non-prose Captain Marvel story, on assignment by editor Ed Herron, written in December 1941.
P.C. Hamerlinck, Captain Marvel expert, disagrees with Dobrotka as the artist in Alter Ego #147 (July 2017); Dobrotka art credit removed by Craig Delich and replaced with a ?.