Original electrical trade vintage catalog for THE MERCOID CORPORATION, was located at 4201 Belmont Avenue, Chicago, IL. Manufacturers of Mercury control electrical switches for heating, air conditioning, refrigeration and various industrial applications. Hermetically sealed, not affected by dust, dirt or corrosion. Disbound from a large 1948 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.