From the 1971 Herman Miller catalogue: "Available upholstered or unupholstered: Fiberglass reinforced plastic/12 colors. Upholsteries: Nilo/22 colors, Vinyl (THIS EXAMPLE)/26 colors, Hopsak/20 colors, Vinyl edge/3 colors."
"Nylon self-levelling glides. Steel tube legs, bright polished zinc-plated with baked on clear epoxy coating. Permanent impregnated fiberglass colors. Base attachment to shell has no bolt heads protruding through seating surface. Also available in wall-guard: specify DSG"