I have been doing land deed research in Chester County for about 10 years now. When you reach back to 1750 and before many land records were referred to as a patent. Depending on how many times a piece of land was bought and sold, a patent reference can be found in the late 1700's also. *** Many land patents during this time were recorded in Patent Book A. I can tell you that Patent Book A is missing. It is not in Chester County, it is not in Philadelphia and it is not in Harrisburg (state capital) Quite a few people have tried to find it over the years but it has not yet shown up anywhere. Sharon Chester County PA