Essentially the same design is also used on the Issac Berlin/Easton rifle and very similarly on the 'two tail dog' rifle. It's an interesting characteristic and could certainly warrant additional investigation insofar as determining if there are any fine idiosyncrasies evident in each version - tool methodology or any particular quirk of design - that might allow attribution. I've seen that same design used elsewhere also; I know I've seen it on one or two other American guns although I can't put my finger on them at the moment, and I've seen it on quite a few German guns. I suspect at it's root it was a common German decorative form of a particular region or era and it carried over into design work here, probably of the 1760s through 1770s or possibly even as late as the 1780s - all the pieces mentioned are somewhat fluid in their dating without more examples to use as a basis for comparison.
While some have referred to the unsigned piece as an early 'Lehigh,' many others tend to view it as an earlier Bucks Co piece and I'd personally view it more in that light. It has a similarly unsigned sibling, obviously the same guy and probably of the same period, but with a slightly more "Bucks" look to reinforce this regional attribution. Same carving around the tang, also. Some mention has been made that they might be early work of Verner - I couldn't say about that, but it's an interesting possibility.
Edit: the super-carved John Moll rifle believed to have been made for Isaac Greenleaf uses it also.
