Here is a short video I shot last year of a Darley Model 2 "mushroom" siren in Etna, California, a small town near the Oregon border. Although it is thought to contain a Model 2, the pitch it is sounding suggests either overvoltage or six ports.
http://www.youtube.com/watch?v=tZy4HTxvNhg
This one was taken on a cheap camera in Turner, Oregon, and is a dual-headed Darley. On a clear day, I once heard this siren on the mall of the state capitol seven miles away in Salem.
http://www.youtube.com/watch?v=CqEB4qBtplw