Original electrical trade vintage catalog for THE MERCOID CORPORATION, was located at 4201 Belmont Avenue, Chicago, IL. And at 205 East 42 nd Street, New York, NY. And at 3137 North Broad Street, Philadelphia, PA. Manufacturers of Mercury automatic control electrical switches for the home and industry heating systems. Disbound from a large 1952 electrical construction materials book, this unique old one page technical specifications brochure would display wonderfully matted and framed. A marvelous addition to your retro electric equipment library.