MARVEL MYSTERY COMICS #24 didn't have a Kirby cover but it DID have 7 pages of Kirby/Simon art making Kirby's third year drawing funny books his most successful so far. He had 14 covers published and 616 interior pages! If THAT wasn't enough to satisfy that era's Kirby fans he also had 19 pages of story illustrations in three different Goodman pulps!!!
It was the third Kirby cover to appear on a comic with no Kirby interior art. This brought Kirby's total for his second year as a professional comic book artist up to 5 covers (all of them inked by Joe Simon) and 121 interior pages.
Besides working for Lincoln Features in 1938, Kirby was also employed by Jerry Iger and Will Eisner's syndicate. His first assignments were Count of Monte Cristo (4 episodes or 8 episodes - its a disputed point between comic historians), Diary of Dr.Hayward (12 episodes) and Wilton of the West (12 episodes).
When Fiction House Publishing contracted Iger and Eisner's syndicate to supply material for JUMBO COMICS they provided them with Kirby's Diary and Wilton which Fiction House used in the first three issues of the title.
The enigmatic Lincoln Features, which was run by Horace T. Elmo, is a syndicate that sold features to weekly papers. Weeklies are a notoriously bad market, and Elmo never had a great deal of luck selling his material. Lincoln was a curious mix of slapdash and brilliant work. The syndicate's main claim to fame is that Jack Kirby got his start there. Unfortunately Kirby didn't discuss the syndicate in any depth in later years, so we really don't know much about it. Some of the Lincoln material is so rare that it has yet to be found actually appearing in a newspaper (Kirby'sAbdul Jones, for instance, so far exists only in the form of a run of proofs that Kirby held onto) - source http://strippersguide.blogspot.com/2011/05/obscurity-of-day-detective-riley.html
Strippersguide.blogspot.com explains that when you DO find a Lincoln strip in a Weekly it usually only runs for only 4-6 episodes which means that the syndicate sent the newspaper some samples, which the Weekly would then use without any intention of picking up the service on a paying basis.
I don't know if this example of Kirby's early strip work appears in EVERY Kirby biography but if you've read Mark Evanier's KIRBY KING OF COMICS or Greg Theakston's JACK KIRBY TREASURY you've already seen this strip.