Proceedings of the 1984 Trade Gun Conference has a section discussing these earlier rifles. It's a good read, but I don't really agree with Shumways dating of the earliest rifles. He maintained that the early Wilson rifle was earlier than the Grice example, but if you ever see them side by side the two are nearly identical, except for the patchboxes. DeWitt Baileys book sort of makes the point that they were contemporaneous with each other. Also I have an early Grice rifle that was either restocked or was made from parts that were imported. It's still a very early style and has both Grice and Wilson markings on the barrel.