I got this!!!!! LOL I don't remember the brand but I remember the heater. I'm still using HOB heaters that were from that same time period.
This is an old submersible heater. The "window" that has the little light is the pilot light window to show you when the heater is actually heating. The light should not be on all the time.
With some old submersible heaters, you had to pinch then turn the knob inside to raise or lower the temps. You could never move the internal knob all that far in one pinch which was to help reduce overheating. See if the knob in pic#2 is squeezable. If it is ( and I believe it will be
), turn the inside knob in the direction as shown to either raise or lower the temp.
If you want to test the thing before putting it in a tank, you can carefully do it. Plug in the heater, twist the knob until the pilot light goes on and wrap your hand around the lower end of the heater. It should start getting hot immediately or within 30 seconds. IF it gets hot, remove your hand and unplug the heater immediately and place it on something that won't burn until it cools off. THEN you can put it in the tank and 15 minutes later, plug it back in. IT IS VERY IMPORTANT that you don't put the hot heater in the tank of colder water or the glass will break and the heater will be worthless.
The biggest downside to these heaters was that you don't know what temp they are set at until you see the pilot light go out. It means you may be needing to go into the tank and readjusting the heater a few times until you get it where you want it. I strongly suggest you do this in a bare tank or in a tank with no fish. This way, if you overshoot your intended temp, no fish will be harmed in the process. Once you have the temp set, unplug the heater and move it back into the main tank (once it's cooled down), wait the 15 mins and replug it in. PRESTO, you should be set.
Hope this helps