SEMCO mercury switch 106MS. Rated for 1.5–110 volts AC or DC. Without housing on millimetre graph paper
<a href="//commons.wikimedia.org/wiki/User:Medvedev" title="User:Medvedev">Medvedev</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>