Is this a real antique with a DC generator?
If so,
Starter relay numbered 1-4 from left to right.
1 - to solenoid energize terminal on starter
2 - hot 12 volts battery
3 - to generator armature terminal
4 - to neutral start switch on top of trans
It works by using the generator armature as the ground but after the motor starts the armature is not a ground anymore and it will prevent the starter from working if the key is turned while the motor is running.
If the relay is clicking but starter not turning try jumping terminals 1 and 2 and the starter should turn. You could probably do away with it if you just connect wires 1 and 4 so the power coming from the neutral switch goes right to the solenoid when you turn the key.