Corner Chair by Thijs Rinsema
I’ve featured a similar corner chair earlier as if being designed by Theo van Doesburg, a member of the Dutch Stijl Group of which Gerrit Rietveld and Piet Mondrian were other members. It seems I misread the tags in the Belvedere Museum then. These photo’s I took at the Gemeentemuseum Den Haag (or The Hague Municipal museum of modern art) recently and I’ve added the tag which shows the The Hague Museum as the owner of the chair. They should know best the provenance of their chair.
Thijs Rinsema was not a member of De Stijl, but was a good friend of Theo van Doesburg and did know Gerrit Rietveld.