unique and seldom found c. 1915-18 antique american industrial wall mount "contact-making" mechanical and/or analog clock designed and fabricated by the minerallac electric co., chicago, il. the clock was designed to provide a reliable and automatic mechanism for making and breaking an electric circuit at regular periodic intervals. the clock was developed for special use with maximum-demand indicators, signal-bell systems, grain-sampling devices, etc. the electrically wound lock is operated with standard line voltages and does not require any batteries. a convenient motor-winding feature eliminates daily key winding. the clock itself is a seth thomas, eight day, key wind with a jeweled balance. there are two main springs; one operating the time mechanism and the other the contact mechanism. the clock is mounted on a black enameled cast iron circular base enclosed with a heavy glass dome or protective cover. the dial hands are original and intact. measures 7 3/4 inches in diameter, 5 inches in height.