single highly sought after original late 1870's oversized american industrial exterior city of chicago illuminated vault light sidewalk panel fragment designed and fabricated by the brown brothers, chicago, il. the refinished fragment is comprised of thick cast iron that has been brushed, lightly polished and sealed with a clear coat lacquer. the existing sun-purple circular-shaped glass insets are mounted tightly within the closely spaced openings. the slightly raised "nubs," configured in sets of six surrounding the glass insets, provide traction and minimized wear and/or damage to the glass insets. multiple sections were recently acquired from chicago sidewalks undergoing extensive rebuilding. unlike the richards and kelly vault light fragments, the lenses used in the brown brothers fragments contain manufacturer markings, in the form of embossed lettering on each and every lens. the chicago-based brown brother & company founded their vault light business in 1860. by 1873, the well-established company boasted a workforce of 85 men at their factory complex, located at clinton and jackson streets. a year after the great chicago fire, the brown brothers installed two miles of sidewalk and/or vault lights throughout the city. the company later changed its name to the brown brothers mfg. company, where they became the ''sole manufacturers of hyatt's patent prismatic "cement" and "lead band" sidewalk lights and vault lights, floor lights, sky lights, and vessels' deck lights.'' 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.