Brian, You have a Signal Stat unit. First thing I would do is pull the bulbs, clean up the bases and the sockets then put a test ligh on the terminals and see if you get a light. If not start at the unit itself and see if you get a light there. Check each wire to each bulb.
If the unit is OK change all the rear wiring, it probably needs it anyway wspecially if it is the old cloth covered wiring.
Ibelive there is a tech article on signal stat units in Tech Tips,if not google it and you will find out what you need.
