IIRC there was an STH-10C found some time ago on the ARS, so the thought of an STL-10C wouldn't be too far fetched. I don't have the photos on hand, so if anyone can find it that would be great! Sidenote: you would not be able to simply slap a 3T22 intake onto an STH/L-10. The rotor on the STL is m...

Yes, Reno had five 500-DHTT sirens, I believe they were sold off to Storey County around 1990 when they stopped testing them. I was only able to find 2 former locations.
Jessie Beck Elementary school
Washoe County Courthouse

Here's a photo of a man standing in front of one.

Yes, it's gas powered.

These are really cool pictures! The sound clarity on these sirens is amazing.

I only know of two. Washoe County Courthouse, and Jessie Beck Elementary School.

Here's a picture of a Colorado Springs 500-DHTT. I think this photo is from the late '60s

Yup, those are Cobreflex speakers, used as PA. Custer uses those on his sirens.

Here are some 500-DHTT pictures from Yonkers, NY.
Yonkers had 10 of them, I made a completed map of all the current and former locations. Here's a 1967 500-DHTT from Reno, NV. Reno purchased 4 of them.

Nice find! From what I know, Albany, NY had three striped jailbar Thunderbolts. They were at: Albany County Supreme Court building, William S Hackett Middle School, and the police department at Western Avenue and W Lawrence street. They were installed in 1952, none of them remain sadly.

I think it was St Joseph Michigan, the Donald C Cook plant had about 14 Hurricanes. Here's a photo of the Hurricane being installed.