Atomic energy was all the rage in the 1950’s. It had ended World War II, there was talk about using it to power cities, and schoolchildren had to duck under their desks regularly in case of nuclear attack. Knowing a good thing when he saw it, A.C. Gilbert (inventor of the Erector Set) decided to release the Gilbert U-238 Atomic Energy Lab to the world. The full set came with a Geiger Counter, a Wilson Cloud Chamber (this would let kids see alpha particles move around – cool stuff!), something called a Spinthariscope… and four chunks of Uranium-238.
The product was only on the shelves for a year before people realized, hmm, maybe it wasn’t a good idea to let their children play with radioactive material. The sudden preponderance of gigantic preying mantises everywhere may have been a factor as well. Exposure to Uranium-238 has been connected to all manner of debilitating illnesses, so it’s quite possible that the lucky tots who woke up early on Christmas morning and got the energy lab as a gift experienced cancer or leukemia later in life. Probably not the science lesson that their parents had intended.