Horn identification help please

Hi everybody I can use some help.I bought this brass air horn at a flea market. The seller didn’t have any info on it and there are no markings on it what so ever.
It doesn’t work and I would like to get it to. The questions I have are, what is it? how much smaller should the hole in the diaphragms normally be? should the trumpet stick into the chamber at all and how much of so? Thanks for all your help !