This obviously came from a Dynamo cabinet. That's a load resistor next to the power supply. Some Dynamo cabinets were shipped with that to provide a minimum load on the power supply as some gameboards did not draw enough current on the +5 volts line to get the power supply to start up consistently.
That black cable should be the 120 vac ouput from the power supply to power the rest of the cabinet. Should be a black, white, and green wire terminated in a 3 pin white Molex connector. Power coming out of this connector is controlled by the power switch on the power supply. This power output cable was intended to go to a power distribution block in the game cabinet where the fluorescent light fixture, isolation transformer power input, and dollar bill validator (if fitted) would all connect. Remember only the monitor is to be connected to the output of the isolation transformer.