Here is an exceptional K&D "Rex" bi-polar dynamo electric motor, a great piece of early electric history. This old stand-by is equiped with 2 cast iron flywheels and it runs like a top. It has a bi-polar field magnet wound for 2 to 6 volts and the commutator has copper "strip" brushes. At the base it measures 3.75 inches by 2.5 inches and is 3.75 inches tall.