• Publication month from James A. Corrick, ''Double Your Pleasure: The Ace SF Double''.
• The Universe Maker is 138 pages; ©1953
• "An ACE Original" on the cover. The first Ace Double.
• The artist is not credited, ORBAN is on the artwork
•
The World of Null-A is 182 pages; ©1945, 1948
• Cover has "Complete and Unabridged"
• The artist is not credited, no visible signature; credited to Meltzoff by Ace Image Library and Meltzoff's website
• For individual, clear images, see
here for
The Universe Maker and
here for
The World of Null-A.