One of two ashcan produced that did not secure the trademark of title and logo.
The other is Flash Comics (Fawcett, 1940 series). Features early version of Captain Marvel, Captain Thunder.
Unable to secure trademarks for Thrill, Flash, or Captain Thunder, Captain Thunder would be renamed as Captain Marvel. Thrill and Flash renamed as Whiz Comics.
The eight-page origin story of Captain Thunder essentially corresponds to the first seven pages as published in the first issue of Whiz Comics (#2) with the 13th and final page of the full story.