When I worked on the London Stock Exchange, a collegue showed me a stunning chess machine that had been sold to him cheaply by a client. It was a regular chess computer but what made it special was the board. It was about 1987 and I don't remember it well. It must have costs thousands originally.
The board had some depth to it – an inch or so – and in that layer void operated an electric motor and sliding levers connected to a magnet. Above a thin wooden board were the pieces – all with magnets or ferrous material in the base.
One made a move in the regular way and then waited for the chess computer to respond. The response took the form of one's opponent's pieces sliding across the board - apparently by themselves! My friend demonstrated how pieces taken, would miraculously slide their way off the board, manoeuvring between other pieces!
I have never seen one before or since.
Does anyone know any more?