Has anyone ever seen Frank Zappa's fretless guitar? What did it look like?

It's pretty cool if you know how to use the Ebow right -- otherwise it can make an awful racket! A good demonstration for anyone interested:

 

I had one and was shocked at the volume increase when you used it. It wasn't just a slight increase, it was massive.
Later they made a model with a switch on it which took the volume right down so there wasn't such a huge jump in volume.

 

The only one I ever saw belonged to a friend-of-a-friend who was in a jazz/fusion/prog type band and for one song he'd whip out the Ebow. The effect was great. Afterward I asked him about it and he said it took him about six months before he had the guts to use it in public.

 

Ebows are pretty cool with fretless guitar, I've also got a baritone fretless equipped with a Fernandes Sustainer and a Yamaha 2000 fitted with a sustainiac.
If you want to see what Frank Zappas Black Widow Acoustic fretless looked like, there is a picture on my website, Unfretted, here:
http://www.unfretted.com/history/history-1970s/