very rare and seldom found original 1840s-1850s oversized early hyatt-patented cast iron and prismatic glass new york city sidewalk vault light lens. the exact fabricator is not known. the origins of illuminating large iron panels with the use of several solid glass rondels or "bullseye" lenses dates back to 1845, when new york city-based inventor thaddeus hyatt patented an illuminating "vault cover" for sealing off the openings above brick-lined building vaults that were located directly beneath city sidewalks. the perforated iron panels containing several closely spaced lenses allowed natural light to illuminate the vaults below during the day. multiple protruding knobs, (arranged in different configurations over the years) were designed to protect the convex-shaped glass lenses from excessive wear and tear. the illuminating covers would become hugely successful in major cities across the country well into the 20th century.