These are vintage midcentury freestanding modular shelving units designed by Poul Cadovius and sold by CADO. The wood is teak. This set includes four sections that have been discretely modified to fill a five-section space. My grandfather purchased them in the 1950s (ish) while he was stationed in Germany and he kept them until his death. I have owned them for the last eight years. I am happy to provide more pictures upon request.