An odd beast, this one. It's even got David over at Pong Story stumped. It looks like an electronics lab bench power supply or multimeter and bits of me wonder whether this was in fact the case originally. When you open it up you're expecting a whopping great big circuitboard in there, but because it uses the venerable General Instruments AY-3-8500 'pong on a chip' the circuitboard is tiny....it's probably only that size to make positioning the switches easier!
It apparently dates from 1976 and there's a huge amount of nothing about it on the web....well, according to google anyway :) I've left a floppy disk in front of it in one of the pix below just so you get an idea of how bloody big it is!