On sale date from the publication date found in the Catalog of Copyright Entries, Part 2, Periodicals, New Series, Volume 34, 1939, Number 4. Class B periodical. Copyright number B 428672.
Cover is signed as can be determined, but it is possible that it was meant to be signed as Leo E. Morey, but was signed hastily causing letters to me missed (m) or look differently (g instead of o, x instead of y).
Script and letterer credits courtesy of Terry Gustafson, son of Paul Gustavson.