[barrysloate]

Most of the sets you cited have something in common: in almost every case, whatever players have survived are either unique or darn close. Nearly every player known in Four Base Hits is unique, although we know of two Mike Kellys. Just So has about a dozen catalogued players, and maybe one or two of them have two examples known. I also believe that the OJ California League players are unique, although perhaps there is a player with two known cards.

The question I have is why have so few survived? You would have to think a fair number of them were distributed, so why are they so terribly rare? I don't know the answer.