If you were a kid or teenager between the 1950s and 1970s, then you might recognize this object. Although it looks strikingly similar to a bottle opener or some sort of woodworking tool, it actually had quite a different use during these years.

Before modern versions of roller skates existed, there were roller skates that looked like this. They had to be strapped on over top of the wearer’s shoes, and were made with a metal base and leather straps.

So where does that funny-looking metal tool come in? Well, that metal tool is actually a key. Every pair of roller skates made during these decades came with one, and it was used to tighten or loosen the fit of the skates. Most roller-skaters wore their key on a string around their neck, and if you lost the key, you pretty much had to buy a new pair of skates.

Pretty cool, right? Some of you may be old enough to have used these metal skates and their adjoining keys. They’re definitely quite different from today’s super light, plastic roller skates. If you own a pair of these (and especially if you still have the key), be sure to hold onto them! They could be worth a ton of money one day.