Just found and bought this off ebay. This is exactly the same siren as the one on my deuce fire truck. There is one difference, it does not have a spot light on the front. This siren is brand new... in its box... I bought one, and had my financial conditions been better, I would have jumped on more. Check it out. I know that if I had not bought it, I would have regretted it forever. Price is great considering the condition it is in. BTW, it is not mine and I am not doing this for any personal gain. The link is: NOS 1968 24V FEDERAL SIREN Police Fire Military Hrdware - eBay (item 370295832031 end time Nov-30-09 17:34:00 PST)
It sounds just like it should... Very period correct (I know the answer is lame, but it is hard to describe!!!) If you look on my youtube video
you can see her (spotless) sister perched on top of the left fender. I planned to have an audio recording going simultaneously to the light show, but my camera could not handle the sound level. I will try again in a few days with a different camera (one that has manually adjustable sound levels), at night, and in full motion. I was just blown away by it being available on ebay. I was afraid that should mine take a d..p, I would be s.o.l. since I did not believe that they were made in that great a number (at least not in 24 Volt). Our local FD in MIami still has mechanicals as well as the electronic ones. In my deuce, when the 2 are blasting, you can hear this one's sound cutting through.
I just thought that if you have a MV that carries a siren, more than likely this is the one. The 2 fire trucks on the November cover of Supply Line magazine have a "variant" of this siren with the spot and the "directors or aimers" on the sides of the body.