It's not really Unique Per se, it's more of an oddity. In Bellevue, Pa. there is a Siren at the top of the VFD inside of an enlarged Copula, presumably an early Model Sterling X10 or Decot Siren, and am unsure if it is still active, let alone still there. There is a video of one of Station 108 Engines (Bellevue) Rolling out for a house explosion and in the very beginning of the video, you can hear the siren atop the FD, Quickly drawn out over the sounds of the Radio and the Engine's Model Q2B
Video:
https://www.youtube.com/watch?v=kNdw_lJRtoc
Street View: (Barely Visible)
https://www.google.com/maps/@40.4969081 ... ?entry=ttu