original oversized c. 1920's vintage industrial heavy duty cast iron steam valve diaphragm holder and/or bonnet salvaged from the boylston factory (chicago, il). the bonnet has a large base plates with flange containing pre-drilled holes. thoroughly cleaned and treated with a clear coat lacquer. great looking surface patina. ideal for repurposed bench or table base. fabricated by the boylston steam specialties co., chicago, il. only one remaining in stock (in this size). measures 18 1/2 x 14 inches.