Herbert Levine spring-o-lators, circa 1956-57.

Beth Levine was the designer for shoe label Herbert Levine (her husband). She created the spring-o-lator after observing a pair of men’s boots that came with an elastic liner which helped prevent the foot from slipping. To prove the spring-o-lator worked on mules, she ran across a hotel lobby during a major convention to show disbelievers that the elastic would help keep the feet in place.

Source: Robyn Michaels