Welcome to the forum, Tomahawk.
Fascinating knife. I, also, wonder about the age of this thing. There appears to be some oxidation present, particularly in recesses on the blade. If truly as old as the seller claimed, this must have been cleaned.
I understand Native American artifacts, particularly weapons, often command staggering prices. If you got a
really good deal, it might just be too good to be true.
I think Tom Hyle has some experience with NA weapons, hopefully he will spot this and comment.
Andrew