First mention of Daily Planet in comic book.
This is the first story with Luthor. Superman asks "Who is Luthor?" The second Luthor story appeared in Superman #4 (cover date Spring 1940). Luthor says "We encounter each other once more".
However Superman #4 may have gone on sale before this issue. In their copyright registration, Detective Comics, Inc. said Action Comics #23 was published Feb 23, 1940. An in-house ad said Superman #4 would go on sale Feb 15; the copyright registration said that it was published Jan 23. Officially, per DC Comics web site, Luthor's first appearance is in Action Comics #23.
Luthor has red hair.
The last panel of this story is an illustrated promotional ad for the Sandman in Adventure Comics.
Title is given in panel 3, page 1 of story.
Writer credit added and art verification by Craig Delich.
Title of strip given as "Tex Thompson".
Letterer credit added by Craig Delich.
Moldoff signs on the final page.
Page includes many small ads from stamps dealers.