The Slinky's first sale was 400 units in 90 minutes at Gimbels in Philadelphia on November 27, 1945 — a dollar each, all gone.

On the evening of November 27, 1945, Richard James set up a slanted board at Gimbels in Philadelphia and let a coiled spring walk down it. His stock of 400 Slinkys, a dollar each, sold out in ninety minutes.

The Slinky did not begin as a toy. In 1943, Richard James, a mechanical engineer working at the Cramp shipyard in Philadelphia, was developing springs for a device the Navy could use to steady equipment aboard ships. One of the springs fell and kept moving, flipping end over end across the floor.

James spent about two years testing metals and proportions until he had a spring that would reliably walk down steps. His wife, Betty, went through a dictionary looking for a name and chose "slinky," a word for graceful, sinuous movement.

Ninety minutes at Gimbels

Nobody knew whether a bundle of wire would sell. Gimbels, the big department store on Philadelphia's Market Street, agreed to let James demonstrate it during the 1945 Christmas rush.

On the evening of November 27, 1945, he showed shoppers how the Slinky could walk down an incline. According to the Encyclopedia of Greater Philadelphia, his stock of 400, priced at $1 each, sold out in ninety minutes. Smithsonian Magazine gives the same 400 and the same dollar price, gone in under two hours.

The Jameses set up James Industries and began making Slinkys in earnest.

The patent and what came after

James filed his patent, titled "Toy and process of use," on August 21, 1946. It was granted on January 28, 1947, as U.S. Patent No. 2,415,012.

When the Slinky was inducted into the National Toy Hall of Fame in 2000, more than 250 million had been sold, according to Smithsonian Magazine. It began with a naval spring that happened to fall off a shelf.