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.
Will Eisner created the Espionage feature, and Will Erwin was a pen name used by Will Eisner (Erwin was Eisner's middle name) until he left the feature after 1940. It also became a house by-line as well for future writers.
Writer revision from Jerry Iger to ? by Craig Delich 2013-12-26. The Who's Who indicates that S. M. Regi was a pen-name sometimes used by Jerry Iger, but also by others as a house by-line. It further indicates that Jerry Iger did not write this feature, but that Alex Blum, under this pen-name or by-line, did draw the strip.
All Gustavson credits verified and courtesy of Terry Gustafson, son of Paul Gustavson.