The 4M blower is smaller which probably costed less, and the lower pressure put less strain on the siren. That's my guess at least.

You are correct, that is an E.A Laboratories Sireane Jr. From my research, some came with 12 ports and some had 8. Awesome! The wiki only says that they only come in 8 ports. Does that help with the year it was produced in? That's a mistake that's been fixed. The 8 vane, 12 port config is unusual a...

12-port only, because they use the Federal STH-10's core albeit flipped vertically to resemble a Model 5 core.

That's what the first gen FS&S 500-SH basically is. The Thunderbeam as well, technically. https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Flive.staticflickr.com%2F3422%2F3907633370_c777c64ba2.jpg&f=1&nofb=1&ipt=841736e5693893b79f2b1fb59694178a22863a61df50bac2a7a15fa04c3975...

It's been done numerous times. There's an STH-10 mounted upside down, a pair of first gen Federal Type Mach. Bs, a Sireno vertical, and a few others come to mind. https://media.discordapp.net/attachments/1157756572068483252/1232143534870626354/unknown.png?ex=663245d6&is=6630f456&hm=a12022fc9...

It's a Sterling 5VX.

Heath was so ahead of his time with his sirens, the rotors are like an STH-10's but 40 years before the STH-10 existed. And this had two of them!

That's a C2 1/2, C1s don't have an eyebolt.

Airhorns such as the Diaphone use a vibrating diaphragm that's actuated by compressed air moving through it. It's quite similar to how our voices work, air moving through a diaphragm to create vibrations which result in audible sound.

Looks like the period at the end wasn't being added to it, I'll fix the link. It should work now.