Does anyone know what this is?

Hi everyone, My name is Phillip and I was recently given this horn from a family friend. He said he had it for at least 25 years so I know its older that that. I did some research and I think its a old 50’s model Leslie A75 but Im not sure. It has Leslie two piece diaphragms. None of the modes look like this but the model numbers match up kinda. I want to put this on my F250 but if its super rare or valuable I wont. Im hoping someone can help. Any ideas? Here are the images. Just copy and paste.


A couple things I’ve found, and you might have seen them already:

From what I can tell, they are 1950’s era Leslie’s, and I wouldn’t use them as they could be quite valuable as they look well cared for.

Use the Horn and Whistle board (first link) and ask those gents over there. They are the end all be all of knowledge when it comes to the older horns.