Grey,
"I THINK", but I'm not sure, that there should be a disk with two contacts inside the narrow end for the bulb to make contact with. I don't see it in the pictures. The disk would be on the bulb side of the spring.
The wire from one side of the switch goes to the bulb, the other side to the power source positive side. The other wire goes to the power source neutral side.
The switch is always in the positive wire.
Looks like that one is missing some of the parts, or I'm not seeing them.
Joe