Dan,
I'm surely no expert on this field, more like a rank amateur. But I can see some likenesses between the Chief's Grade Trade Gun and fowlers of the period. And I could surely be 180 degrees off on that thought.
That's my thought and it's worth what you paid for it. Zero, nada, zilch.
By the by, on my vacation, I picked up a pretty nice North Star West Trade Gun in 12 gauge. I think it will be fun to shoot. I have always had a liking for a .715 round ball.
I'd post some photos of it and a few other things, but I forget what program I use to host images.
John (Bigsmoke)