Used in conjunction with the 1938 motor drive tuning knob.
models: 9S204, 9S232, 9S242, 9S244, 9S262, 9S263, 9S264, 9S365, 12S205, 12S232, 12S245, 12S265, 12S266, 12S267, 12S268, 15U246, 15U269, 15U270, 15U271, 15U272, 15U273
Dimensions: 1-28/32" diameter, 3/4" tall, fits a 1/4" shaft