*VERY* hard to find:
http://www.ebay.com/itm/Federal-Sig...094?pt=LH_DefaultDomain_0&hash=item1c4985ddae
http://www.ebay.com/itm/Federal-Sig...094?pt=LH_DefaultDomain_0&hash=item1c4985ddae
In my opinion, you can't compare a 66L with a C6B, since they are two different class of sirens. Also, you have to give consideration to the mount, which is extremely rare, and by itself, will probably command $125 - $150 from the person that needs it. You can find many sirens, since they made so many of them, however, when it comes to coach specific mounts, they are extremely rare to find with the siren. Remember, "todays crazy prices are tomorrows bargains!"
I know that somewhere in my garage, I have a restored C6BR with that mount, that I purchased from John Dorgan, a number of years ago. I only wish that I could find it, so I could turn it into cash to fund my next restoration.