WH did not make gas dryers until the straight front design, but many of their electric dryers could be used on 120 volt service. Maybe this one just has a 120 volt cord on it and the seller thought that it was a gas dryer.
Probably about as fast as "Warm" setting on the Wards gas dryer by Norge that used a 1000 watt electric element to provide heat on the "Warm" setting. Of course, with the Norge's airflow, it might have been faster.
So were WH dryers of this era manufactured to switch between using 120/220 volt by changing the wiring connections inside? If the dryer is currently set up for 120 usage is a simple connection change internally all that's necessary to use it on 220? Or did they manufacture two different lines of dryers: 120 & 220 volt?