It's been a while since I saw the inside of my friend's, but I do remember each key has a contact switch on the back, similar yet different from an organ but with wooden keys. I think it's an FM keyboard. I will know more soon when I prepare my friend's for sale. I don't have any way to post pictures here but I will take pictures when I clean it up. The only thing I remember it needing is the output Jack needs to be replaced.
I think it's a similar sound to the old RMIs and Gulbransens piano setting, but I am relying on old memories. This keyboard has no other sounds. It's heavy, so they don't fetch top dollar.