late 19th or early 20th century original brushed and sealed bare metal early american industrial city sidewalk perforated coal chute cover fabricated by the richards and kelly mfg. co., chicago, il. the unique vault-light manhole cover features a deeply incised strongly geometric radial pattern with circular holes arranged along the outer perimeter. none of the original glass lenses remain. the "chicago" manhole cover served as an access point to an underground sidewalk basement typically consisting of stone slap or brick arch construction. the subterranean space was primarily used for the storage of coal that was consumed as residential and commercial fuel. the prism glass inset lenses provided natural light in an otherwise dimly lit or dark space. salvaged from a chicago commercial building block in downtown chicago. several chicago coal covers available. measures 18 inches in diameter