The question I'm asking is whether a Mears 2- wire thermostat, circa 1985 that controlled electric baseboard heating elements, had a build in frost proof protection safeguard that would not allow heat to go below 40 or 50 degrees. Beige, round setting dial.

Exact model number?

Mears Model # M401

Sorry I show no listing in my electronic catalogue for that number but there is a M401-25 number but it offers no description.

I will say that most BB thermostats did not offer a specific setting for frost proofing. In most cases you would just turn it down to accomplish that.

How do you trouble shoot the mears m401 therostat