Sometimes vendors would like to sell relatively high-value items in vending machines. That is, merchandise worth more than a candy bar. Nowadays that's not a problem because there's technology that can scan paper currency or read credit cards, making larger transactions possible.
But back in the 1960s, vending machines relied on coins for payment, so selling high-value merchandise wasn't practical. Especially since the machines could only measure weight, shape, and size to determine if the coins were real — and these characteristics are easy to fake with low-value blanks.
The British printing company Thomas de la Rue devised a solution: radioactive vending machine tokens.
Its researchers realized it would be possible to create tokens made out of layers of radioactive materials such as uranium and carbon14
. These tokens would emit unique radioactive signatures that could be measured by Geiger counters inside a vending machine. Such tokens wouldn't be easy to forge. The company patented this idea in 1967
I'm not aware that any vending machines accepting radioactive tokens were ever put into to use.
I imagine they would have suffered from the same problem that plagued other efforts to put radiation to practical, everyday use — such as the radioactive golf balls
we posted about a few months ago (the radiation made it possible to find the balls if lost). The radiation from one token (or golf ball) wasn't a health hazard, but if a bunch of them were stored together, then the radiation did become a problem.
Nashua Telegraph - Jan 11, 1967