OK, so what is the Boomerang? It received its name from the fact that it always returns to the exact original setting after scanning a wide range of harmonics. The Maestro Boomerang is not only a wide range wah wah pedal but also a volume pedal. It's deemed as one of the best wah pedals ever built - and I totally agree. The only other wah that comes close is my Electro-Harmonix Crying Tone.
If you happen to own either a Boomerang or Boomerang II and you are in trouble with it, Joe Gagan is the guy to talk to. His knowledge about these pedals is exceptional and he offers the right parts you may need. The replacement pot as well as the replacement bottom plate of my Boomerang are Joe's supplies.
02/15/2017: entire set of early Boss pedals for sale, all silver screw, mostly transparent switch, mostly boxed, many come with instructions too. For details please inquire: e-mail