By now you must know I have nothing but love for the Commodore 64. As a kid I cut my teeth on the full gambit of Commodore machines from the VIC 20 right through to the Amiga 3000, but there is no machine that brought me more joy than the C64.
The C64 revolutionized the home computer market in North America. I dare to say that it was more a games machine and was never taken too seriously for business use. It lacked some of the needed features for professionals like a numpad (unlike it's big brother the C128).
There were various third party numpad units you could purchase and connect to your C64, but never one like this.
The Rotary Dial Numpad is exactly what is sounds like; a rotary telephone style numpad for the Commodore 64. Why you ask? Why not.
Jan Derogee decided he wanted to fill a hole that no one has ever thought of filling and set out to build a rotary telephone style numpad for the C64.
The unit is electronics free. Besides the two push buttons for "Shift" and "Enter", the internals contain some micro limit switches and a modified servo. The servo motor isn't used as a servo at all. The electronics have been completely removed from the servo and it is used for it's gears and motor only.
In order to not overload the joystick port on the C64, Jan wired in a few AA batteries to power the motor when the dial plate is released and is returning to the idle position, so the batteries are completely disconnected when the device is not in use.
You can find everything you need to build your own Rotary Dial Numpad including STLs for the 3D printed parts, labels for the unit and the needed C64 driver software on Jan's project page.