[J.Max]

Horn looks like a Conn to me, or it could be a King. Definitely not a Selmer or SML. (Or Buffet, which I suppose might be the other choice.) It could be a Buescher, but I've never seen a Buescher with a neck like that. (Look at how the octave key is attached.) I've seen him play both...

Does anyone know if he had an endorsement deal? His band was pretty popular...