Like George said, I tried a bone saddle once on a Prismatone years ago, and didn't think it sounded as good. I think the nylon saddle insert is part of the sound.
Phil, I always wondered about "Harper Valley" too. It's a very distinctive sound.
Bill, Willie plugs direct into an old Baldwin amp, the one with all the pushbutton switches. It has a channel just for the Prismatone.
Craig