I was telling some friends today about when I went to the New York Worlds Fair in 1965. In one demonstration, they had a box set up with radioactive material in it behind thick glass. You gave the man a dime and he dropped it into a slot and through the glass you could see it roll back and forth down the box, coming out at the bottom. They then passed it in front of a Geiger Counter to show you your dime is now radioactive. Then they put the dime into a plastic holder so you could walk around with a radioactive dime in your pocket.
I wonder if they did any long-term studies on us lucky fair-goers.