I have a Setson hat patiented in 1878 Trademarked The Fray. Where would I find more info on this subject?

Take it to a western memorabilia shop and have it appraised and insured. The appraiser should be able to give you some information and you can always write to Stetson yourself, since they are still making hats, they will likely have an archive where they would be able to look for information on the specific stetson you own.