When I first made it home with my F100 I couldn't find a button for the horn, even though I could see that they were in place under the cowl. Eventually I noticed a big, black button bolted underneath the dashboard. Thinking that I found the horn I pushed it and damned if it didn't produce a loud Wolf Whistle. I almost fell out of the truck laughing. Still haven't found the real horn button though. Guess I'll have to fabricate one.
When I moved to Omaha in 1980, Jubilee was still in business making those and other horns. I also have one. Got mine at a swap meet for a dollar...gotta keep the little impeller lubed or it'll seize up like mine did...soaked it in penetrating oil and it's good as new.
They don't seem to care, my boss grabbed mine when I wasn't looking and put air to it and it sounded the same to me. Still pissed me off though.