You can see the heat gradient by the coloration on the copper coil. The top I would say at some point got over 600 degrees F.
I didn't remeber this particular stove having a thermostat persae but instead a manual air damper control. I used to have an 80s VC Encore that had the true thermostat control.
It's funny in the book they call it the "primary air Thermostat handle" but in the exploded parts diagram I see nothing that looks like a coiled up thermostat device. I think it may be a misprint from the older models that had a true thermostat.
Here is my 80 gallon solar tank (indirect with a coil on top and a separate coil on bottom) that I bought new/used for $500.
My controller, domestic and solar loop expansion tanks, heating zones, etc.
View attachment 169187
Caleffi MX LTE solar/whatever controller and data logger (same as a Resol iSolar BX)
9 inputs for temperature, 2 Grundfos direct sensor inputs, one irradiation sensor input, 4 powered output relays, 2 PWM outputs, and 1 dry set of contacts. Can be connected to the Internet via Vbus.
View attachment 169188