Bought this old stove recently and have started a renovation on it. First job was to try and pull the dent out where the riser had been pushed into the tank as can be seen in the above photo. I decided to try and fill it with water and freeze it and push the dent out from inside so to speak. New washers on filler cap and reserve lid to seal it then into the freezer for 8 hours checking on progress every now and then. I obviously did not get all of the air in the tank replaced with water as there was a hiss of escaping air as I removed the filler cap. So full pressure was not brought to bear on the dent by expanding ice. But some of the depression was pushed out as can be seen in the second photo, below. I could try again but have decided I can live with it rather than risking blowing the tank up!