My personal feeling is it could be put into service. It’s common enough and is just another example of an old horn not tied to any specific place or time. Your challenges will be sealing it and deciding how to put a strap on it.
I would use cutlers resin to seal it because the gaps look substantial. I melt and mix pine pitch, ground charcoal, beeswax, and sometimes ground herbivore manure (horse or deep droppings) to a gooey consistency, slather that into the crevices, hit it with a heat gun and let it fill all the cavities. You can clean any over-runs with turpentine after it cools.
