Rich: it's Chambers' Classic American, I think that's what it's called. It's a large Siler rather than the smaller one. I needed the depth in the lock plate. I rounded the tail a bit and filed the tail flat. I also reshaped the cock to give it a bit more of a pigeon breasted look, and rounded the pan. The rifle I'm emulating used an English lock.
I'm looking forward to carving this stock. It's a nice dense piece of walnut, and the reference rifle has both incised and relief carving, as well as some interesting scalloping along the butt stock lower moulding.