almost every series has at least 1 district with small total printings. On top of that, almost every district of every series has a small print run within there respective total printings. Then you have the serial numbered notes to look for - Ladders, Radars and repeaters - along side the other fancy serials that some folks do like to collect. There are notes with small margains, large margains ect I would highly suggest some currency books. The 2 i like the most are the Friedberg book on US paper money and the Swartz/Lindquist book Small sized US paper money. There are other compilations for us notes too that are worth picking up like the Comprehensive catalog os US paper money, and several others. Any book that lists printings and other varieites is worth picking up!!!
Two recommended books Since you have a lot of questions about currency you should start getting some reading materials to help you along the way: Standard Guide to Small-Size U.S. Paper Money - 1928-Date Ninth Edition, by John Schwartz (Author) & Scott Lindquist (Author) A Guide Book of United States Paper Money 2nd Ed. (Official Red Book) Arthur Friedberg (Author)
I agree with krispy on these books. I basicaly sleep with them due to how much I use them, especially the Standard Guide.
Sorry, another one to get that encompasses all large and small size notes, along with fractionals, MPC, Phillipines, and other varieties is the Standard Catalog of U.S. Paper Money. I'm including a link here: http://www.amazon.com/Standard-Catalog-Paper-United-States/dp/089689939X/ref=pd_sim_b_1
