From the Museum of Atomic Toys:
This was the most elaborate Atomic Energy educational set ever produced, but it was only only available from 1951 to 1952. Its relatively high price for the time ($50.00) and its sophistication were the explanation Gilbert gave for the set’s short lifespan. Today, it is so highly prized by collectors that a complete set can go for more than 100 times the original price.
(via PCL Linkdump)