five matching original and nicely worn solid glass "brown brothers" city sidewalk vault lenses or insets utilizing characteristics of vault light inventor hyatt's patent. the sun-purple color glass lenses were originally set within perforated cast iron panels with surrounding knobs or nubs designed to protect the glass from excessive wear and/or damage. the underside of each diminutive vault light lens contains manufacturer markings lightly embossed along the outer perimeter of the backside. the lenses are free from cracks or breaks. several lenses available in various condition. 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. priced for the lot of five.