What you see in the photo shown above is the top-side view of an old Justice League of America comic book — issue No. 196, with a cover date of November 1981. As you can see, there’s a green mark along the page edges, as if someone had swiped a green Magic Marker against the top of the book.
But if we flip through the issue, it quickly becomes apparent that no Magic Marker was involved. Instead, each page has been imprinted with a green bar that bleeds off the top edge. Here are some representative examples:
That comic book comes from the collection of IC reader Norb Rozek (who, as you may recall, previously told us about the surprisingly inconsistent street sign typography in Green Bay, Wisconsin). Some of his other comics from that same period are imprinted with similar markings, but often in different colors, including purple, black, blue, and red:
Justice League is a DC Comics title, while The X-Men is published by Marvel, so the colored bars weren’t specific to one company. They were also used by other publishers, including Archie Comics and Harvey Comics. You might assume, as I initially did, that the printer added these marks as a form of color control and/or registration, similar to the colored dots frequently seen on consumer packaging. But that’s not the case.