My big thing was an Atomic Ring, around 1950? or so.
Supposedly it was a tiny scintillometer in a little tube consisting of a tiny lens
supposedly focused on a little screen with "atomic material" embedded in it that would make the screen sparkle when an atom decayed. Just like in the atomic bomb.
This all was mounted on an adjustable ring.
Instructions said to use it in a dark room and allow yourself to get used to the dark.
Well, I stayed in the dark for a while, looked into it, no sparkles. Stayed in the dark for a longer while, still no sparkles.
Stayed in the dark for a still longer while, still no sparkles.
Never did see any scintillations in it. And I hadn't been that dark-adapted since just befpre I was born.
Terry, 230RN
ETA I can't believe they're still selling the darned things.
https://www.ebay.com/sch/i.html?_nkw=kix%20atomic%20ring