I have a need for this knob to finish up the restoration on a nice Gilfillan Bros. model 521 - T
The knob set is made up of a small knob (for the tuner) and three larger knobs (on/off, band switch and tone)
They are not lettered so that is not an issue
I have two of the large ones and the one small one but I need another larger knob.
I will buy one or if you have a set that you do not wish to split up, I will buy them all.
It accepts a full round shaft with a set screw and has a metal insert. It is 1-1/8" wide and 11/16" with fairly distinct pattern on it, kind of like a raised bullseye. I will attach a few pics so you can have a visual reference.
here are pics of the knob: