This is a longshot, but I thought I'd put the feelers out just in case.
I don't even know how many episodes of Concentration from the early 70s exist in people's collections. My friend and coworker's father, who has since passed, was a contestant on Concentration some time in the early 70s. She and her family are fuzzy on the details such as the exact date, but we do know he won a minimum of five games. I don't know how common five-time champs were on the show, so I don't know how much that helps. His name was John Krauss.
Hoping to strike lightning in a bottle. Anybody with early 70s episodes of Concentration in their collection wanna check for a John Krauss? I'd appreciate it.