There have been a lot of systems that no one ever knew about, simply because they never amounted to anything. On the same note, like the Hitachi Saturn, there have also been alot of systems that are just different versions, lisenced out to different companies, a lot like the Panasonic Q.
Also, in places where pirating is more rampant there is plenty of home-made consoles or rip off consoles. You would be very surprised by all the different pirated versions of the NES.