This link will give you quite a bit of information to get started.http://stampsmarter.com/1847usa/1847Home.html
The Washington/Franklins have many varieties based upon design, perforations, watermarks, and printing type. They take some study to be able to distinguish between them but this is a challenge that many hobbyists enjoy. Explore the Stamp Smarter site, is has hundreds of pages of information and is totally free. Alternatively, you could see if your local library has catalogs and/or purchase some.