The coiled metal toy that walks down stairs began life as a failed scientific endeavor. Marine engineer Richard James was trying to create an anti-vibration mechanism for ship instruments in the early 1940s. One day he knocked over a delicate experimental spring and watched in amazement as it crept, its coils fountaining, down a stack of books, onto a table, then to the floor. He found that it was especially good at descending steps.↵
Seeing the spring as more than a passing curiosity, James and his wife borrowed $500 and started a production company for a toy they called Slinky. Using a homemade machine, they coiled 80-foot sections of steel ribbon into the first Slinkys, and during Christmas 1945 debuted the toy at Gimbels department store in Philadelphia. Nervous about how the toy would sell, James lined up a friend to buy the first one. He needn't have worried-within 90 minutes he had sold 400 Slinkys. Since then, more than 300 million Slinkys have been sold. Though they started as a scientific failure, the flip-flopping toys have proved useful in a number of ways.