Original heating trade vintage catalog for GENERAL GAS LIGHT COMPANY, was located in Kalamazoo, MI. Manufacturers of the Humphrey Gas Unit Heater. Used in shop and factory heating, as an auxiliary to an existing heating plant, intermittent for warehouse, churches, stores and drying processes in factories. Model No. 100 and 200. Disbound from a large 1931 industrial heating catalog, this unique old one page technical brochure would display wonderfully matted and framed. A marvelous addition to your retro heating equipment library. Slight damp stain on outer edge.