via this auction
"That thing is called "Mini-Synth" and I must really be extremely rare. It is probably something like an effect unit for guitar or something. Power supply must be installed as a 9V battery.
And how does that sound now? Difficult to describe. Is probably something simple like a synthesizer for guitar?
If you put into it when a guitar input and the whole thing connects to the amplifier, well, I'd say the guitar signal in such a way Square wave and converted into three separately controllable .... Broken octaves or so. Then there there's a hard-soft switches. Since I do not really know what you want, for me it sounds more like a loud-soft.
I think that was once intended as a substitute for synth-guitar bands.
The unit has a sturdy metal casing and looks pretty good, I would say almost as good as new. Perhaps what strange effect devices for collectors.
Another note for the fashion-conscious guitarists: You can wear the chic device at the belt! (At the back are hooks)"
See the T.Danko label below for more.