Very interesting research and thank you for the information.
Based on what you provided, if I were you, I'd contact Charlie Justmann at checkpointcharlies.com. He's a good friend of mine, and we've done a lot of business over the years. He buys a lot, and also does consignments. He is very fair at both. I feel he's the best "online dealer" out there. (not to knock the others you mentioned though, as I know 3 of the 4 you mentioned). Hope this helps.
Matt
