From your photos, it looks like a nicely made rifle. I see in the second pic that there is a tag on it that says, "Hawken flintlock 50 cal." Forgive my jumping on this: it no more resembles a Hawken than a Lada resembles a Lincoln. It is simply a half stocked flintlock rifle. But once you are past that, it is still a nicely made rifle that will give you years of pleasure, both in shooting and in just adding it to your stable.
I see it has a John Clark lock from Tottenham Ontario. Parts for this lock are no longer available as far as I know, but the one I had was a decent lock. Replace that piece of brick or whatever is in the cock's jaw's (barely) with a real flint, seated right back to the jaw screw, if you please.
If the bore is good, and the price suits you, buy it without regret.