The Letron MC-3 is a wide-spread keyboard with an interesting 16-step sequencer for the drums. You can programme your own beat with it and set a previously chosen auto accompaniment (from one of the 8 preset patterns) to it.
The drum sounds are beautifully digital, the bass and chord sounds consist of sawtooth waves. The minimal melody sounds are, again, highly reminiscent of the Commodore C64 sound chip. This so-called MC-3 hardware was built into many different "no-name" products with most different casing forms. They're easy to get and cheap on ebay.