Seems to still be a 'thing' you can buy without any checksMid 80s
you could still order them from RS components, but then you would have an account, I think it was to stop the cash sales, lots of older cars used them to trigger boot lights, I think I have a few tucked away someplace
I guess the mercury switch was more reliable and easier for unskilled people to use than to fabricate something
we also found some very very old Smoke detectors in Bristol that contained some very radioactive stuff, which rather upset my boss as he had not budgeeted for the disposal costs of the detectors, associated wiring, and the paint scraped off the ceiling above them, plus the masks and paper suits, think they went to the National Physical Laboratory in the end, Radium was the main component, not sure how much, but not the sort of thing to get in the wrong hands
Glass bodied switch in a blue ABS housing with slotted fixing holes (39mm F.C.)Max. carrying current 2APrewired with 300mm of 2 core PVC cable.
Radium 226 is still used in smoke detectors without any associated clean-up costs after the ten year life expectancy of the source