Got it! Along with two other collections from the same series about Muddy Waters and Memphis Slim, and Lightnin Hopkins, Brownie McGhee, Sonny Terry and Big Joe Williams. Very good, though I still haven't listened to the other two. The T-Bone Walker alone is 3 CDs.
And the Mabern must be something else. I once saw him in a jazz cellar here in town accompanying the Eric Alexander Quartet.