After failing as a an anti-vibration device for military ships the inventor marketed his little metal spring thing as a toy. After more than 50 years of production using the original machinery in Pennsylvania, enough Slinkys have been made that the miles of wire used is said to be enough to circle the earth 126 times. 250 million of the $1.99 toys have been sold.
In 1999 the U.S. Postal Service featured the toy in its “Celebrate The Century” commemorative stamp program. The stamp design shows a Slinky in the classic play position, straddling a step.