Smith and Stone Lighted Mercury Switch

These were common in the 70s in higher end construction as a silent alternative to the commonly used snap switch. Instead of a mechanical switch contact, the toggle on these tilted a small glass vial containing a bead of mercury. When the switch was switched on, the glass vial was tilted so that the mercury bridged a set of contacts at one end. Aside from light switches, mercury switches were also commonly found in older thermostats, and trunk lid switches.

Fears of mercury leakage more or less killed these off. This one is a NOS find from Restore.