Graphic Mouse
Potentiometers, drive belts and an adjustable working area in place of familiar encoders.
The most hardcore mouse mechanically.
Its sensors are potentiometers with fixed minimum and maximum positions. An adjustment on the underside lets you align the screen boundaries with the mouse's virtual working area.
A belt drive! And the belts haven't dried out over all these years, as they usually do in audio equipment. Have a look at that pressure spring, too.
There are no brains inside. Electronically, this is more of an analogue joystick than a conventional mouse.
It all looks like a prototype, but quite a few were produced under different names and with different button colours. This version is for the Apple II; Commodore versions existed as well.
