I'm not sure if this thread is only for cards from a certain era (because I don't see any cards listed not from the 90's), but what about the Topps 2007 no name/no team fronts? Topps Vault released them in Beckett holders with blank backs and labeled as 1/1's, but some got into circulation with proper backs. I don't know how rare they are, but I've seen less than 5 of Fielder's on ebay. I have two myself...here's one (regular base on left):
If this is not "on topic" I apologize.
If this is not "on topic" I apologize.