This lamp operated on 4 amp DC series street lighting circuits in the 1908-1925 era. As far as I know there are currently only two examples of this arc lamp that have survived although tens of thousands were produced. This lamp is also a form of magnetite lamp. It employs a copper electrode and a magnetite electrode to produce the arc . These were used principally in the cities of Pittsburg and Denver. This unit was used historically in Pittsburgh wile the other surviving example which resides in the Georgetown Energy Museum in Colorado was historically used in Denver. Here is a look at the General Electric version of this lamp [id=618976274] The offical name for the GE Magnetite lamp was the Luminous Arc Lamp. Westinghouse referred to theirs as the Metalic Flame Arc Lamp.