This may be the switch my dad once installed in a 1960-vintage car of his, as part of a rudimentary theft alarm. The switch was mounted on the underside of the hood. Opening the hood, or moving the vehicle, would tilt/jiggle the switch causing the horn to sound.
I'm not sure why my dad was so theft-conscious; Toronto in 1960 was not exactly a major centre of urban crime. Perhaps he'd been reading Popular Mechanics magazine, or some such American trash.
Anyway, mercury is neat stuff -- a metal that's a liquid at room temperature. The mind boggles.
When I was a boy, I had a pill vial with a bead of mercury in it that had been salvaged from a broken mercury thermometer. I'd take it out from time to time and roll it about in the palm of my hand; I thought it a fascinating thing to observe.
'Explains a lot, possibly.
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I'll stash this in the box where I keep spare, miscellaneous switches.
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