The Electric Service Supplies Company, or ESSCO, was a manufacturer of high-quality parts for trolleys, interurbans, and subway cars. The company's Keystone Line of products, which included a patented trolley pole catcher, were considered industry standard. They were often supplied as factory equipment by manufacturers such as J.G. Brill and Co.
This high quality booklet is a reprint of a brochure created by ESSCO to promote their products in the 1920's.