Generic Knob for 1930's Radios

The knobs use a set screw (included with knob) to fix them to a shaft. The smaller knob is just a hair larger in diameter than a quarter. Used by Detrola, Truetone, possibly others. The larger of the two is used mostly on consoles and some table models.

Dimensions of small knob: 13/16" wide, 1/2" tall, 1/4" hole
Dimensions of medium knob: 1" wide, 9/16" tall, 1/4" hole
Dimensions of larger knob: 1-1/8" wide, 5/8" tall, 1/4" hole