Theres a tiny chance that in really really old microwaves, that they could have a Mercury switch to turn it off if it got tipped over.
I do think that thats not very likely. They did have a huge amount of safeguards on the first microwave ovens.
The other possibility would be 'Mercury wetted' Reed switches, & breaking one open by accident, then maybe cutting yourself on the glass, since the Mercury probably wouldn't do much anyway.... Lol.
The early microwaves had Gold plating on one end of the magnetrons Copper cavity. I have only seen one microwave of this era though.
The Aluminium cooling fins around the Magnetron are Cast Ali or of a radial design, probably the same units that were made for Microwave RADAR equipment, just sidelined for home/commercial cooking use.
Also the Magnetrons have a radioactive Thorated ( Thorium metal ) coated Tungsten emitter electrode.
Its possibly enough radioactivity to set off the Scrapyards radioactive materials detector if its not in the microwave.. or theres a bunch of them in one place.
Its not dangerously radioactive, its the same stuff that was in the older Gas lighting mantles to make them brighter. It helps 'shake off' the light.
Same as shaking off the microwaves.
Also used on some TIG welding electrodes, it helps 'shake off' the arc & stabilises it a bit. Not as common now because any tiny bits of it show up in the weld test Xray photos.
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