Amazing video! Don't know where the design originated, but very similar cassette carousels were also made in Yugoslavia. I just got a pair of those today. I was searching something about these on can they be stacked together somehow so I stumbled upon this video.
So weird: yesterday I was looking up Finnish vocalist Tapio Wilska and I accidentally clicked the auto-complete result for Tapio Wirkkala. I had never heard of him before so I skimmed the summary paragraph on his Wikipedia before continuing on to what I was originally doing. And now today I stumble across this video and hear about him again! What are the chances? Anyway, very neat video, thanks!
Most of what I know of DDR is from the film Lives Of Others. And the hours I spent around Alexanderplatz in 1989. I had a cassette carousel but it was not German. Ugly black with woodgrain vinyl stickers. Threw it out.