He told me that the newer one (bottom) had hardly been used. I don't believe it had a thermostat, when you look into the hole there is no corresponding one in the chassis.
For comparison, here's the iron with temperature dial.
It is a Grossag (of course), only a bit newer. This one is 1000 Watt, 5.5 kg. The axis of the dial goes right through the cover of the iron, so if yours doesn't have a hole there, it hasn't been provided with a thermostat. I assume yours is a Grossag as well, so the factory, when they still produced tailoring irons, seems to have used the same mould for casting the handle assembly.
I don't use the iron much, I'm not really into weight lifting. I generally prefer the lighter and more efficient steam iron. When extra pressure is needed you just add part of your body weight.