Please HELP what's the name of this gadget ???

What's The Name Of This GadGet !!

 I haven't turned on my Commodore 64 in years and found this connector attached to the Joystick. As you can see the original label have been erased over the years of sweaty palms twisting and adjusting this knob. I know what this gadget does that's not an issue. The proper name and manufacturer is what I need. If you know a tech or gaming historian please forward this page to them. Thank you.