I have to agree with the previous assessments regarding the new made consensus of this knife. I would ask the owner to take a look at the spine of the blade, is it the same thickness from front to back, with no taper? If so, that is a common give-away for being of modern manufacture. Also, the design is all wrong for a knife this size. A round grip is virtually useless on a knife like this, because the knife will roll in your hand. Look for some documented antique "Bowies" and you will see they have slab sides, which keep the knife centered in your grip when using it for chopping, slashing, etc. Just my thoughts!
J.