Part number is 27-1084, but those seem to be out of stock everywhere. Stern's part 077-5005-00 (www.pinballlife.com) is a close substitute.

This one will work:

http://www.pinballlife.com/index.php?p=product&id=284

They can be tested with a meter. Disconnect one wire, remove the light bulb, and test across the contacts.

GI sockets do not have diodes.

Usually these short because of contamination (usually solder flecks)

Disconnect the wires from both terminals of the coin door lamp socket and remove the bulb too. Now with your ohm meter set to it's highest resistance scale (on an analog meter) and connected across both socket terminals, there should be NO continuity. In other words, it should read very very high resistance.

If you see continuity or low resistance, the socket is shorted.

Generally, the sockets go bad from the center terminal insulator shrinking/breaking over time (old age) or the socket shell crimp breaks free and the socket shell flops around and shorts to the mounting frame.

You have to remove the bulb and ONE contact's wires.

Otherwise you'll be measuring across the GI circuitry in the power driver PCB, which probably will read as shorted.

Only by removing all the wires from one of the contacts can you isolate the bulb socket from the rest of the wiring harness.

Removing the bulb will also help eliminate any false readings caused by the bulb filament.

To be thorough, you should test the socket without the bulb, test the bulb itself, then test the socket with the bulb installed. All three tests should show no short.