Original data for this issue is from Howard Keltner's Golden Age Comic Books Index.
Last appeared in Our Flag Comics #5 (April, 1942).
Various indexers list: last appeared in Our Flag Comics #5 (April, 1942), or last appeared in Captain Courageous Comics #6 (March, 1942). Art credits from Nigel Cantwell, 8/22/2006.
Last appearance in Super-Mystery Comics, next appears in Four Favorites #8. Last panel says "Capt. Gallant sails north to the Arctic wilderness in the next issue of Super-Mystery Comics!! Brrr-r-r!!"
Cliff Howe name is a byline, possibly Lester Dent, according to Jerry Bails' Who's Who.
Last appearance. Art credits from Nigel Cantwell, 8/22/2006. Last panel states "Vulcan appears in every issue of Super-Mystery Comics on sale at your newstand".