During the Second World War, an engineer in the US Navy, named Richard James was on a new ship, he’d been trying to invent a spring that could help keep sensitive nautical instruments balanced while on rough seas.

He accidentally knocked over one of his experimental springs and was fascinated by the way they ‘walked down’, rather than just falling.

So when he returned home, he made a spring to show his wife and she was entranced, and they decided to make it into a toy.

He spent the next two years figuring out the best steel gauge and coil to use. While his wife Betty, came up with the name ‘Slinky’, which is a swedish word meaning sleek or sinuous.

In 1945, the Gimbel’s Department store demonstrated the Slinky and then again in 1946 at an American Toy Fair. Richard got his friend a dollar to buy the first Slinky, to get people interested.

He needn’t have worried as the entire 400 Slinky’s were sold in minutes.

With just $500, Richard and Betty formed a company to mass produce their creation. Today, all Slinky’s are made in Hollidaysburg, Pennsylvania, using the original equipment designed and engineered by Richard James. Each Slinky is made from 80 feet of wire which folds up in 10 seconds.

The Slinky toy appeared on children’s ‘favourite toys’ list for decades. The Slinky line now includes pull-toys, ‘costumed’ slinky’s as well as plastic and 14-carat gold plated versions.

The non-electrical, no-battery-required, non-video toy has fascinated three generations of children and adults alike. The metal Slinky is different from the original only in that the sharp ends are crimped for safety.

It’s been judged by the The Toy Book to be one of the top 10 toys ever invented. Now you can buy slinky dogs and pets and even one called Crazy Eyes, which has slinky extended fake eyeballs.

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More than 300 million have been sold worldwide and in excess of 50,000 tons of wire has been used since the first Slinky went into production.

If you joined them all up they would encircle the earth more than 126 times.