SOLD:
$75 Paypal shipped for a Certainbass varitone Jazz control plate complete with knobs and ready to drop in. The functions are Concentric Volume/Volume; 6-position Varitone; and Blend.
I paid $138. It is a really high quality piece with many usable sound options. I've found that I'm a "P-Bass" guy and am parting out my Jazz bass.
According to his website, David Certain offers a lifetime transferable warranty on this item: "-Each varitone is tested before and after sealing, and is sold with a LIFETIME warranty, no time limit and doesn't have to be original purchaser. As long as we can tell it's one of ours, we will replace a failed one for free. We have not had one failure out of over 100 Varitones we've installed on CertainBass custom basses."
Please check the eBay listing for a detailed description of the functions:
http://cgi.ebay.com/BEST-VARITONE-EV...item3ca546f7a3 
