May 1, 1940 on sale date confirmed from an online copy at the Digital Comic Museum (http://digitalcomicmuseum.com/index.php?dlid=17986, retrieved June 27, 2015), on page 2 marked with on sale date of May 1, 1940.
Notes:
Credited by a previous indexer to Ogden Whitney. Charlie Chan, Joe Palooka and Marvelo, are depicted on a flying carpet over an urban landscape The heads are lifted from stories by the individual creators (as are the vignettes of The Skyman, Dixie Dugan, Spymaster and The Face), but there is no evidence to confirm that Ogden Whitney drew the rest of the image.