I like it!
For my Design & Technology GCSE project many moons ago, when I was 15
I made an office chair, but fabricated the whole thing apart from the upper seat.
I went to a scrap yard as they were known then, now called a vehicle dismantler, with my dad and pulled a seat out of a Fiat X19, got hold of a couple of bearings, and school provided the steel pipe for the main shaft. The design worked on a screw principle, so you turned the chair round and round one way to increase the height, and the opposite way to decrease.
School wouldn't let me take it home though because they wanted to display it in D&T department entrance
I do fancy making another one after seeing yours