Balans vital kneeling chair (Porlock TA24)

It's old; it's a back support kneeling chair. it's height adjustable and has a lever which I don't really know what it's meant to do. It's an old version of this: https://www.wesjon.nl/contents/en-uk/d33_kniestoel_Balans_Vital.html
           I'm too tall for it, so the padded knee bit gets uncomfortable quite soon.
 Give it a spin!