Back to the Stone Age

From Author Wars - https://authorwars.com/publications/back-to-the-stone-age-248477.html

Overview:

Title: Back to the Stone Age
Author: Edgar Rice Burroughs
Year: Unknown
Publisher: Ace Books
Price: $1.25
Pages: 251
Binding: Paperback
Type: Novel
Title Reference: Back to the Stone Age
Notes: Magazine serial as 'Seven Worlds to Conquer'.
Cover artist is uncredited. Signature is clearly visible in the lower right corner.