At this link you can watch (starting at 6:38) the video that Mastro made for the Lionel Carter collection when he auctioned it off in 2007. It features Carter, Doug Allen, Bill Mastro, and Dave Forman of SGC talking about how Carter decided to sell his collection and how MastroNet and SGC got involved.
https://www.youtube.com/watch?v=50pkXT_UPm0