Wow, Giz, hard to believe that is the same horn in both photo's. Nice work.
Was the horn off white under the original grey color?
Years ago I purchased a horn at a flea market or "Junque Shoppe" for a couple bucks and it was so cheap I didn't look at it that closely. I had been very selective of a couple of items and it was laying close to the counter. When I spotted it, I off handedly asked what they wanted for it and since it was so cheap, I added it to the other items. THEN after getting home, I spotted it was threaded on the spout end. I think it was one of the cheap horns fitted with a cheap mouth piece, though the mouth piece was long gone. So I didn't do anything with it. May have to hunt it back out and look at it again.
Gus