I was 11, and handled the ‘samples’ at a BNFL booth (at an airshow) where a geiger counter was set up, it wasn’t til the demonstration guy returned and demonstrated to someone else how the coin-sized samples set off the counter that I realised it wasn’t a ‘self service’ type demonstration. The samples were labelled with their atomic symbol, and the most reactive samples were labelled as uranium (about 20mm diameter) and plutonium (about 5mm diameter). At the time I told myself they were likely fake, since leaving a plutonium sample lying around wouldn’t be very likely.

I’ve not died of radiation poisoning or cancer yet, but it’s only been 41 years.