Looking at my master project, here are the cards I am going to need that I have on my list as having a combined PSA/SGC pop of 3 or less
Piedmont 350-460/42
Murray (1)
Schlei (2)
Wiltse w/Cap (2)
SweetCap 150/25
Steinfeldt (2)
SweetCap 350/25
There are 22 players here with 3 or less
SweetCap 350/30
Criger (1)
SweetCap 350-460/42OP
Bridwell w/Cap (2)
Chase Blue (3)
American Beauty 350
Shad Barry (1)
American Beauty 460
Bridwell w/Cap (3)
Doyle (1)
Wiltse w/Cap (3)
Cycle 460
Seymour (1)
Old Mill
Beaumont (3)
Devlin (2)
Doolin (3)
Leach (3)
Lumley (2)
Merkle (1)
Rucker (1)
Steinfeldt (3)
Sovereign 350
Bradley (1)
Clarke (1)
I think both of these might be errors, they show up on the SGC pop report but not on the PSA, and t206 resource doesn't list either on their Sov 350 checklist
Tolstoi
Downs (2)
Easterly (2)
Rossman (1)
Broad Leaf 350 and 460
There are 40 players with 3 or fewer on the combined pop reports for the BL 350, and then Cobb Red has 3 combined
Carolina Brights
There are 12 players with 3 or fewer on the combined pop reports
Drum
It is easier to list the players with 4 or more known copies. It's only Jack Barry. And for all I know, its less than 4 because of crack outs/crossovers
Red Hindu
Bridwell w/Cap (1)
Uzit
Crandall w/Cap (3)
McGraw w/Cap (1)
Murray (1)
So, for those who think the pop reports are overrated, if you have raw copies of those cards, I'd be happy to take them off you for a reasonable price
