Is it Radium?
Got this Phinney-Walker clock at a flea market today for $10, and I thought I might have scored a pretty good find.
It’s marked “Made in Germany” on the back and appears to be a genuine vintage clock. The numbers and hands glow, and they get quite bright under a blacklight. Once I remove the blacklight, though, the glow fades pretty quickly.
I tested it with a GMC-300S Geiger counter. My background reading is around 15–20 CPM. The clock usually reads around 20–30 CPM, and I've seen it reach about 40 CPM. Interestingly, I get roughly the same readings from both the front and the back of the clock.
I'm trying to figure out what kind of luminous material this actually uses. Is it radium, another radioactive lume such as promethium, or simply non-radioactive phosphorescent paint?
I've found information suggesting these German-made Phinney-Walker clocks are genuine vintage pieces, and I've also seen similar clocks reported as radioactive. But the relatively low Geiger reading on mine has me confused.
Does anyone recognize this specific model or know what type of lume was used on these German-made Phinney-Walker clocks? Any information on the approximate date, model, or experience testing similar examples would be greatly appreciated.
Really need some sos 😭