I know it was in use in the English language, but does the use of a name with a 'apostrophe' (lack of possessive actually) bother anybody but me? Maybe I'm used to seeing 'His Horn'.
The perfectly round nail head is a 'no-go' for me. A roughly scraped horn without a single 'chatter' mark on it (?) and with well done engraving? The horn displays lighter shades through the middle, evidencing 'wear:, but none at the throat? Opposing/mirror-image pattern cuts that don't match up at this level of art? Do all the crossbars on the 'A's' have the 'v' shape, or are some straight? Can't tell.
The plug appears to be pine and not quite, but close to 'old growth'. Old-ish and repurposed? Pine plug in a fine art horn and a 'North East' horn doesn't ring true. Turning the photo upside down I see a '56' but no '17''? The aged milk paint is over-done, a step too far. The hole I can neither make hair or hide out of.
I think it was an interesting old horn that should have been left alone, but was reworked for/by a re-enactor. I'd certainly keep it, or put it together in a bag and horn display ensemble, or use it for re-enacting, Enjoy it. I just wouldn't make a big deal out of it.
All that said, I would gladly stand corrected in my opinion were it to be proved to be otherwise.