“What walks down stairs,

alone or in pairs and makes a slinkity sound?

A spring, a spring, a marvelous thing!

Everyone knows it’s Slinky.”

Do you remember the first time you saw a Slinky toy? Such a simple design – a wire (or plastic) coil, perfectly designed to walk end over end.

Simple. Elegant.

Perhaps your first introduction was from 1995’s Toy Story, with Ed Varney’s excellently nuanced portrayal of the character Slinky Dog. Maybe you received one as a holiday present, as a child or adult.

As Slinky recently celebrated 70 years since being invented by marine Engineer Richard James just outside Philadelphia, Pennsylvania, and nearly 400 million people have purchased Slinky toys – it’s clear their popularity is enduring.

Here are 6 insights that give a clue as to why they have stayed so relevant throughout multiple generations:

1. It was an immediate best-seller.

To start selling his toy, James asked the famous Gimbels department store in Philadelphia to provide counter space for a demonstration.

In front of amazed customers, he debuted the famous Slinky “walk” down a ramp, end-over-end. They sold out of their initial run of 400 Slinkys in just 90 minutes.

2. It’s been to space.

In 1985, Slinky was part of a weightlessness experiment on the Space Shuttle Discovery. Dr. M. Rhea Seddon found that Slinky behaved differently in space.

“It won’t slink at all,” Dr. Seddon said in a telecast. ”It sort of droops.”

3. It is affordable.

Released initially in 1946, Richard James’ wife Betty expressed a desire to keep the cost of Slinky low so that families of any income could have a Slinky. The Original Slinky cost $1 in 1946, 70 years later is only $4.99, with a smaller Slinky Jr at $2.50. A Slinky Dog will set you back around $20.

“One of the best things about Slinky is it’s popularly priced, and everyone can afford one,” adds Neil Friedman, President & CEO of Alex Brands, the makers of Slinky.

4. It really is for everyone.

Think Slinky is just for kids? Think again!

“It’s the original fidget toy,” says Neil. “Everyone here has one on their desk, and most of their friends do as well. When they’re in stressful situations, you just need to watch it go back and forth and it just relaxes you.”

5. It has practical applications.

While most people treat Slinky as a toy, others have found that Slinky has applications beyond entertainment.

A standard metal Slinky coil resonates as a quarter wave between 7 and 8 MHz when it is stretched to lengths between 5 and 15 feet. Enterprising engineers have found that simply expanding or contracting a Slinky will tune it to that resonance, giving them a cheap and lightweight antenna. US soldiers even started using Slinkys as makeshift antennas during the Vietnam War.

6. It has won a ton of awards.

Slinky is so well-known and beloved that in 2000 was inducted into the Toy Hall of Fame. There have been Slinky Postage Stamps in two different countries. A bill was even drafted to make Slinky the official toy of Pennsylvania.

The Smithsonian Institution even made it part of a permanent exhibition – which shows just how enduring it is.

No matter what your experience of the Slinky, the James’ hit upon something truly special. Their unique, simple, “fun for a girl or a boy” toy has created the type of legacy product that every entrepreneur hopes to achieve.

Everyone knows “it’s Slinky”, indeed.