"The portable 'Calvin Discjockey' could be plugged into any amp or pa system. It was primarily marketed to radio DJs as a convenient console in a suitcase for personal appearances and dances. It played both old-standard 78s and new microgroove 33/45s, using a two-sided cartridge with a knob on the head that flipped it over. Separate volume controls for each turntable and a microphone. No cue channel. The metal platters were covered in soft fiber and driven by a pinch-roller between the inside rim and motor capstans. The white knobs adjusted the speed by moving the roller across the capstan's three diameters. The mic jack was whimsically labeled "Mike". c-1962"
(No link, sorry. Got this from a friend who emailed it to me.)
Back when there were enough radio DJs to create a market that something like this could be sold. Now it would be nearly a hundred thousand dollars and only available to the wildly successful and corporate buyers. Imagine, so many DJs that every city had its own soundtrack. What a time to be alive.