Yes, that's really a quarter in the upper right corner! Mario Marchese, maker of the train set inside a record player case, emailed me about his latest project. This train set, the second smallest in the world, is pulled by a locomotive half an inch long. Mario writes:
They are 1/2 inch pieces cut out of wine cork, painted and embedded with magnets. Servo motor with a cardboard disc guides the train across the the tracks. It's a PWM circuit powered by a 555 timer. The sound comes from a Radio Shack recorder Module.