Tim - The tip is integral to the horn... I've never seen a screw tip on a storage horn this large, and if I had photographed the tip from a slightly different angle, you could see that it bends with the general curvature of the horn. This is a right-side carry horn, so perhaps it was carried at times, but it's so big, I doubt that it was carried very much.
Rich - I'd think this was probably a Pennsylvania horn based on the small, scalloped design at the base and its pleasing form, perhaps about 1800. The high, turned plug is walnut while the tip is faceted, but the throat remains round, so despite the tip's facets I doubt it was a New England horn and lean toward an early PA horn. Let's see what the learned Mr. Crosby thinks!
By the way, the horn has light script initials of "J S M" just above the base.
Shelby Gallien