A portable battery driven mono cassette player/recorder w/speaker, much like the one in the image.
Wonderful to have and impress friends. Great for trips to the beach etc. Also I remember bringing it to sleepover, and recording our thoughts in the dark, as it had a built-in microphone. I wish I still had those tapes.
I was about ten - 1974.
Btw, I remember people, my parents included, would enjoy recording their talks and thoughts around a microphone on a gathering. It was a more common thing to do back then. They used a Tandberg reel-to-reel. I still have a few tapes, some from the sixties.