[C-20] Rudolph the Red-Nosed Reindeer tabloid comic is considered to be the first book of this series, even though it doesn't mention LIMITED COLLECTORS' EDITION (but neither does C-24 nor C-50).
Here are the actual indicia titles for this series:
[C-20], C-24, and C-50: "RUDOLPH, THE RED-NOSED REINDEER"
C-21: "SHAZAM!"
C-22, C-23, C-25, C-27, C-29, C-31 through C-36, C-38 through C-49, C-51, C-52, C-57, and C-59: "LIMITED COLLECTORS' EDITION"
C-37: "LIMITED COLLECTOR'S EDITION" (misplacing the apostrophe; it is correct on the cover)
According to Back Issue #61 (TwoMorrows Publishing, December 2012), Limited Collectors' Edition C-61 would have been another Best of DC issue, with "The Menace of the Dragonfly Raiders" (a Hawkman story from The Brave and the Bold #42), "The Hundred Dollar Deal!" (a Jonah Hex story from All-Star Western #11), "Must There Be a Superman?" (from Superman #247), and "No Evil Shall Escape My Sight!" (from Green Lantern #76); but it was not published.