This issue has variants.
The on-sale date is the publication date reported in the U. S. Copyright Office filing found in the Catalog of Copyright Entries, Part 2, Periodicals, New Series, Volume 34, 1939, Number 4. Second class periodical. Copyright number 429173.
Indicia (transcription courtesy of Frank Motler):
Vol.1, No.1, MARVEL COMICS, Oct., 1939 Published monthly by Timely Publications, publication office, 81 Spring St., Newark, N. J. Executive office, 330 W. 42nd St., New York, N. Y. Art and editorial by Funnies Incorporated, 45 W. 45th St., New York, N. Y. Application for entry as Second Class Matter pending at the Post Office at Newark, N. J. Yearly subscription in U. S. and Canada, $1.50; elsewhere $2.00. No actual person is named or delineated in this magazine. Copyright, 1939 by Timely Publications. Printed in U.S.A.
According to Rip at the collector-society.com boards, the print runs were 80,000 on the October edition and 800,000 on the November edition.
Inside front cover. Five single-panel gag cartoons. Sequence information from Joe Lovece (August 11, 2006). Also includes the indicia.
First Human Torch story. The Human Torch wears a blue uniform in this story. He doesn't adopt the Jim Hammond identity until issue #4.
First Angel story. Writer credit revised from Paul Gustavson to Ray Gill ?. Gustavson was an artist ONLY. Although the Who's Who lists no writer for 1939, Ray Gill wrote the series in 1940 and this story may have been by him. Notes added by Craig Delich 2008-11-2.
First Namor story, reprinted from the eight pages of Motion Picture Funnies Weekly #1 and expanded with four additional pages.
First Masked Raider story. Writer revision from Al Anders to ? Anders was an artist only, and the Who's Who lists no writer for this strip. Note added by Craig Delich 2008-11-2.
Art identification by Dr. Michael J. Vassallo of the Timely-Atlas list. Note that the 3rd letter in the signature's first name is a dense smudge. The Masterwork edition and Craig Delich interprets it as an "h" (Tohm), while Dr. Vassallo believes it is an "m" (Tomm).
Artist name added by Craig Delich 2008-11-2.
First Ka-Zar comics story. Adapted from Bob Byrd's "King of Fang and Claw" (KA-ZAR pulp magazine #1). Writer credit revised from Ben Thompson to ?. Thompson was an artist only and the Who's Who does not list a writer for the strip. Last note added by Craig Delich 2008-11-2.
Writer credit further revised 2013-07-08, adapting a pulp story isn't beyond the skills of any penciler.