I know they're a little earlier than your time frame, but the 1893 Just So Tobacco cards are ridiculously rare. Anyways, I'm gonna have to agree with bijoem and exhibitman, RPPC and team/regional issues are pretty hard to come by. Probably not less than 12, but still extremely difficult.
Here's a website I found with some interesting cards.
http://www.cycleback.com/rarerthanhonus.html