I had asked Bill about the original knobs that came on his prototype and he said he still had one somewhere. Well, he finally located it and sent me a couple of pictures of the knob. To my surprise I see a lot of similarities to the "M" hat knobs.
Bill says that the top of the knob has a metal ring glued to it and that the skirt of the knob had numbers 1 through 9 on it but they had worn off. He had asked Gene about the knobs at some point and Gene said he did not really know but thought they were probably left over from Semie's time at Rickenbacker.
Bill has the original pots from his prototype Celebrity and the pots codes date to mid 1963. I know the prototypes were built until late 1964 or early 1965 so I'm guessing they were pots that Semie probably had lying around and ended up in that guitar.
So, here are the photos. If anyone has additional information or theories, please chime in!
Note the set screw.
This image really reminds me of the M Hat Knob.
