What does the relay switch box show for identification? If Chevrolet, it should have a stamp saying “DelcoRemy, I think. My guess is the horn is half of the set of town and country horns, but the brackets seem to be different than I’ve seen before.
Maybe Tiny will chime in on this. I think I recall his ‘38 has a set of T&C horns?
I don't know if the actual horns were used on more than one application but the bracket rules out the 37-38 accessory car horns.
Save a life, adopt a senior shelter pet. The three main causes of blindness: Cataracts, Politics, Religion. Name your dog Naked so you can walk Naked in the park.