This precision CNC brass fine-focus gear provides a seamless feel and provides a smooth operation of the controls. The gear includes the notched key slots which seamlessly fit into the knob so it can't rotate independently (see photos).
Note: The knob is not included nor is the glue. I suggest using LOCTITE® 648 to secure the gear to the shaft as it's a low viscosity, high strength, anaerobic-curing retaining compound is designed for bonding cylindrical fitting parts.
FYI, I also have a one-piece fine focus shaft available for sale for the YS2:
https://www.ebay.com/itm/292906205718