Is there any other information on the heater? Where it was made; the year? I don't know if this is connected but definitely worth looking into: The Stewart Clark Manufacturing Co. ( chicago/detroit area) used to make horse carriage heaters. As the Chicago Flexible Shaft Co c. 1895 they made sheep/horse clipping equipment. And, eventually, as the Stewart Warner Instrument Manufacturing Co ( aka Stewart Warner corp.) they made instruments for automobiles.