This unique variac type variable AC supply originally was a Precision Scientific lab heater and had an electric heating element on top and used the variac to set the temperature. Years ago it was converted to be a bench supply instead, with the added AC outlets on top instead of the heating element. The dial reads 0-100% so we recommending plugging in a little AC meter into one of the outlets unless you want to do math in your head for the percentage! Or you can relabel the dial Housing is stainless steel! A must have if you test, sell, or restore radios, you can bring up the voltage slowly to help restore the capacitors Otherwise a sudden inrush of full voltage after years of non use, can destroy tubes, transformers etc capacitors cannot handle that and can short out. Also good for a quiet stage light dimmer. NO AC noise that conventional dimmers create. The internal unit says 7.5A which would be 900 watts at 120v or 937.5 w at 125v The dial is labeled 750watt, which I assume was the max wattage of the heating element.