Silver Age Comics: Secret Origins of the Marvel Comics Corners

Silver Age Comics: Secret Origins of the Marvel Comics Corners: "Mark Engblom remarked awhile ago on the top left corners of Marvel Comics, where they had a small image of the lead characters, and the Marvel Comics Group logo and the price. This has been an amazingly durable feature of the comics. When did it start?

Answer: With the May 1963 issues as illustrated by Fantastic Four #14."