The Hewlett-Packard 59307A is an HP-IB VHF switch. It contains two DC-to-500MHz 50-ohm relays optimized for 1ns pulse waveforms.
The front push-buttons contain tiny bulbs for illumination. These can burn out over time, but replacements are still available. The bulbs are 5V 0.06A in a "T-1 3/4 standard midget flange" form, suitable replacements are JKL-7333, CM-7333 or similar.
The "power" and "remote" lights contain bulbs with wire terminals, rated for 6V and 0.04A. These can be replaced with JKL-1730 bulbs or similar.
- HP 59307A VHF Switch Operating and Service Manual (PDF, 2.3MB)
- Peter Holzleitner - Hewlett Packard VHF Switch — a good description of the 59307A and other useful information.