It appears these were sold in the 1950s and 60s.
Photo of real ones.
Youtube video which shows a few shots of them in action, but it's not the exclusive focus of the video.
lol so I watched the video. It looks like there is supposed to be an additional piece at the end of the track that's not in the pictures. It appears to smoothly guide you to the ground, which makes a whole lot more sense than simply dumping you down a six inch drop...