In 1983, there weren't many portable music options. The Walkman had only been out for a few years, CDs were just in their infancy, and most people owned a large collection of records. Audio Technica's Mister Disc was designed to fill this void.
What probably seemed like a great idea turned into a flop. They're almost impossible to find now, even on ebay (here's an old listing). I guess us 80s kids just weren't cool enough to see the intrinsic greatness in the Mister Disc.
via Soul Express Radio
By the way there also were ghetto blasters equipped with an vertical tray for a 12-inch record.
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