NGC has a Numismatic Encyclopedia section up on their web site - check it out if you are interested in Numismatics!
The reason I was looking for this information, is my son is collecting both the State Quarters (both Mint Marks "P" and "D") as well as the Presidential Dollars (from both Mint Marks), thus I was looking for why the Presidential $1 coins have two different designations for the two different orientations of the edge text orientation (i.e. Date, Mint Mark & Motto is incused in the edge of the piece). PCGS Price Guide for Presidential Dollars refers to these two orientation as "Position A" and "Position B", while other references refer to the different orientations as "Type 2" and "Type 1" respectively.
I've posted two images of the James Monroe $1 Coin, one of each of the two different edge text orientations; each image has been annotated with both designations to help make this clear Position B or Type 1 and Position A or Type 2 up on my flickr account (they are in the Macro set)