Need advice on replacement for 1960s thermostat that controls radiant ceiling heat

Hi,

I'm looking for advice on a suitable thermostat to replace an old (circa 1967) thermostat that controls radiant ceiling heat in a bedroom. For context - the house has multiple thermostats that control ceiling heat in different areas of the house. The one I'm wanting to replace doesn't seem to turn off i.e. even when turned all the way down the ceiling still feels warm. The original thermostat has 'Electric Living' on the cover, though I'm not sure if that's the actual brand. In a couple of rooms it looks like the thermostats have already been updated with slightly more modern 'King' brand thermostats.

Based on review of existing posts on this site, I believe I'm looking for a line voltage thermostat. What I can't figure out is whether I need 120 V or 240 V. Unfortunately, the heating system doesn't appear to have it's own breaker on the electrical panel - it seems to be combined with the kitchen range for some reason. This makes me think that 240 V is what I'm looking for.

Please see attached photos of original Electric Living thermostat with and without the cover, plus a picture of one of the newer/replacement King thermostats. In the photo of the original thermostat without the cover, I did wonder if the small screw that is visible on the front of the unit (inside the circular cutout) maybe allowed recalibration of the thermostat but it doesn't want to turn in either direction, so I'm guessing replacement of the entire unit is the way to go.

Any advice would be greatly appreciated. Thanks!