I was given an old aquarium heater by a family member, it is a Supreme Heetmaster Mod II. She knew nothing about it, as it was second hand to her as well. I tried reading up on it, couldn't find anything about other than the fact that it is OLD.
So, I figured I would test it before I just throw it in a tank and hope for the best. I filled my water change bucket up with approx. 3 gallons, pulled my tank thermometer and put it in the bucket, and set the heater up in the bucket as well.
As of right now, the thermometer reads 74°F The heater is not plugged in as I read you should wait to plug it in until it gets accustomed to the water temperature. So I will update this as I progress with this test.