The FD in the next town south of my place (Melville) used to have *years* ago an STL-10 as one of their satellite whistles. This one had a slightly faster wind-up and achieved full-cycle for about 10 seconds before easing back down. It was junked when I was maybe 15 (I'm 36); so it must have been a venerable oldie.
Maybe this one was programmed to fast wail or something...