Phosphor

I use to collect Depression Glass, red Fiestaware, and natural ore. I would bring one of the Geiger counters to a flea market to make sure the item of interest was real before buying it.

ooooo why do you have a Geiger counter? They aren't that common, most people wouldn't even recognise one 

They must be turned off, cause I would have expected them to pick up on background radiation 

Preppers usually buy them in case of nuclear war; but in my case, I use to be really interested in nuclear stuff in my teens. 

I store them with the batteries removed, since alkaline batteries are notorious for leaking. Background radiation around here is about 20 counts/min. The yellow model has as radioactive sample on the side for field checks. 

I still have all of my samples and stuff, so I may post some pics on here.