Check this out! I drove past this the other day. I literally had no idea it (and the old Model 5 next to it) existed despite my extensive map of the county (Ulster; check the link in my signature), so I was pretty hyped to find it. I think it's the old Highland fire house. The new one has a recently repainted Model 2, and station 2 has an STH-10.
I don't know a whole lot about Denver sirens. Isn't this model called the Duplex? There are other models as well, aren't there?