The basement workshop has needed attention of late. Lots of legacy robotics stuff, Barbie Jeep parts and suchlike - must go in order to make space for new robotics components. I imagine in a few years those will be obsolete too. It's the way of technology. Sic Semper Recyclo.
Plenty of oddities have turned up including this gem. I actually can't call it a mystery, as I know why it was down there. As to it's earlier story, difficult to say.
It looks like, and in fact is, a Geiger counter.
These used to be somewhat commonplace items, but now you mostly see them in old movies. The staccato clicking when it is held up and waved around was the universal sound of Nuclear Dread back in a day when the prospects of a US/USSR holocaust were on the minds of all.
Here's a few small details that help us pin down the history of the item at hand.