Thanks for your opinions and observations.
As you said C2Cigars, I'm wary whenever the world's sole source of anything is a single eBay seller, albeit one with a pristine feedback rating. I'd previously purchased a red set for my PC (if they're homemade they're very good), yet there's a fresh one currently for sale. If these are so rare that they're not available elsewhere, I can't see how one could amass so many of these without making or taking them.
Not surprisingly, the official Upper Deck checklist doesn't provide any useful information. I don't think there's a better resource than TCDB users, especially when completeness and accuracy of checklists are concerned.