I will tell you that one thing I have definitely learned thus far is to preserve the provenance. For years, once the TPA put the signed card in the case, the value of provenance was significantly diminished. The card once entombed was supposedly forever authentic just because a TPA said so. Who needs the letter enclosing the card from Fred Snodgrass when that happens? Auction houses have been separating letters from cards, and throwing the envelopes into even another lot because the player wrote his last name in the return address.
The 2018 Spring Steiner Auction had four signed T206 cards in it from a wonderfully large through the mail collection. Steiner broke the entire collection up and failed to share the evidence of where the cards were obtained, by whom, and how. Did you know, for example, that the baseball address list that the collector used to find his ballplayers was also included deep in the auction, as just a random, soulless vintage baseball player address list?
http://auction.steinersports.com/lot-104975.aspx
There was space for a “description” like “This is how our consignor of hundreds of TTM autographs found his players” but instead it was left appallingly blank. I spent several hours today combing through two different Steiner Auctions to piece back together the fabric and soul of this collection, which by the way happened to include four signed T206 cards. I’ll post more about it when I complete my research.