As far as I know, it has only been sold in Japan. There are rumors that most parts of the circuit are very close to Bob Moog's EM theremin design, the predecessor of the Etherwave Standard.
I received one to review years ago, and unfortunately I could never get it to work. The power supply that came with it wasn't grounded, and the builder suggested I wire up a new ground from the theremin to the wall. It wouldn't stay in tune. It's a shame, because the cabinet has nice aesthetics in my opinion.