On sale date from the publication date found at the Catalog of Copyright Entries, Part 2, Periodicals, New Series, Volume 35, January-December 1940, Numbers 1-4. Second class permit. Copyright number 437459.
AC Comics editor Bill Black identified the art in in this strip as being by Will Eisner. Larry Antonette drew Yarko in 1941 according to the Who's Who. Writer/art credits revised from Bob Powell to ? by Craig Delich 2010-1-10 since the Who's Who does NOT list Powell with any credits for Yarko and Powell did NOT use the pen name of Anthony Brooks [according to the Who's Who], nor did Eisner use the pen name of Anthony Brooks.
Writer credit revised from Munson Paddock to ? by Craig Delich 2010-1-10. The Who's Who only lists Paddock as artist on this strip.