Lovely. Horns with recessed throats are not typical of North Carolina, but I think I've seen pictures of one or two found there- IIRC, Grant shows one associated with the Winston-Salem area, and I think Briggs might illustrate one (perhaps the same one? I've never cross-referenced the two books...).
It looks pretty dark for an engraved horn in the pictures, and pretty uniform, with no color change between body and throat. If that due to aging, the photography, or was it a amber or green horn originally, due you think? I've been wondering about the possibility of engraving naturally amber horns, given the difficulty of finding good white horns these days.