PSA Ranks them based on mixture of price and scarcity on a level from 1-10, with 52 unranked simply because they are so scarce. I would recommend taking this with a grain of salt.
Jesse Burkett is a 9 and Jack Chesbro is a 10, and i have seen a total of 2 combined autographs of theirs in the last few years that I would call legit, while Barney Dreyfuss is unranked and I know he is around and not as scarce as other unranked individuals-or Jack Chesbro for that matter.
http://www.psacard.com/dnasetregistr...tion.aspx?c=37