This Collins 75A-4 Original 4 to 1 Spinner Knob & Vernier Gear Drive are in excellent condition. The gear drive is very nice and runs smooth. The spinner knob has both set screws.This tuning knob and drive set are VERY difficult to find!
To install you simply remove the original knob and the two screws that hold the shaft bracket, remove the shaft bracket and install the vernier drive unit and knob.
I will include a copy of the instruction book.