Seven-inch singles produced in the US had a large half-dollar size hole in the center, unlike the tiny hole punched in LPs that fit conveniently onto a turntable spindle. This large hole tradition was originally instituted in order to accommodate the mechanism inside a jukebox. Rather than making a separate version for home use, the simple solution was to sell adapters that popped into the center of a 45, making it playable on a standard record player. These gadgets were usually found in a bin near the checkout at every record store, a dozen or so for a dollar.
[Read the article to bring back memories of Fotomat booths, tube testers, and more!]
(via 11 “Modern Antiques” Today’s Kids Have Probably Never Seen - Mental Floss)