These were all the rage when they came out some 23 years ago or so. They were specifically made for DJs who were used to shuffling carts in and out of cart machines. The idea was to use familiar motions and procedures so DJs could easily perform their shifts using CDs without relearning studio dynamics. The only downside, a DJ could remove the CD that was playing by accident whereas pulling a playing cart out of a cart machine is difficult to do. Later Denon versions made it more difficult to remove playing CDs.
This is a promotions photo circa 1987.
This machine is still in use 22 years after its manufacture date. Over the years the top cover has been removed countless times, no doubt to replace the KSS-210A optics and bearings or to periodically clean them. The Phillips head screws are so worn a screw extractor is nearly required.
They are located under a circuit board, which has to be removed. Again, the DN-951 series CD players did away with this, making maintenance easier. These CD players could and often were affected by RF especially when the studios were co-located with an AM transmitter site. One such symptom was randomly speeding up and slowing down while playing. It made for some interesting-sounding songs and even more interesting commentary by the morning show.
Every time the optics and bearing were replaced, there was a pretty involved alignment procedure that took some time to get right. I remember some funny Japanese-to-English translations in the service manual.
Of course, nowadays if there are any issues, you just chuck the computer and get a new one.