On sale date from the publication date found in the Catalog of Copyright Entries, Part 2, Periodicals, New Series, Volume 35, 1940, Number 2. Class B periodical Copyright number B 447071. Reported as issue #4 to the Copyright Office. One sale date confirmed as February 23 in the promotion advertisement for this issue on the back cover of Master Comics (Fawcett, 1940 series) #1. See https://publicrecords.copyright.gov/application-card/CC19381945B_446000-447999.1072 for more detail. Copyright renewed 1967-06-01 as RE 411109 from Catalog of Copyright Entries, Third Series. Part 2: Periodicals Jan-Dec 1967: Vol 21, page 406.