The blue diode is marked "DB4, X449" as far as I can tell.
The components on board are marked "R", "D", and "C" (I assume, resistor, diode, capacitor). The micro-switch which controls the circuit is an Omron D2MC-5F (photo below).
Phil
I'm hoping to reproduce a speed control circuit. It powers a 110v AC universal vacuum cleaner motor which is installed in an old-time payer piano. The electric suction motor overcomes leaks in the old foot-pump player piano. It's designed to provide two, pre-set motor speeds; a high-speed for...