Another is DC's LIMITED COLLECTORS' EDITION, which likewise magically begins with issue 20, and it's anyone's guess what would explain the missing previous 19 issues.

The series changes title to ALL-NEW COLLECTORS' EDITION for issues 53-56.
Then back to LIMITED COLLECTORS' EDITION for issue 57(WELCOME BACK KOTTER).

Back to ALL NEW COLLECTORS' EDITION for 58 (SUPERMAN VS. SHAZAM, by Buckler).

LIMITED COLLECTORS' EDITION for 59(BATMAN'S STRANGEST CASES).
Then back to ALL NEW COLLECTORS' EDITION for issue 60(RUDOLPH'S SUMMER FUN).

Then FAMOUS FIRST EDITION for issue 61 (r SUPERMAN 1 from 1940).
Then back to ALL-NEW COLLECTORS' EDITION for issue 62 (SUPERMAN THE MOVIE, photos and articles about the 1978 movie, on glossy paper)!


And of course from a few years prior, the FAMOUS FIRST EDITION Golden age replica editions, which also double as LIMITED COLLECTORS' EDITION issues.