Empire Comfort Systems TMV Wall Thermostat Millivolt Reed-Switch.
This thermostat can be used with GWT-25, GWT-35, GWT-50 Gravity Vented Wall Furnaces and is one of several optional thermostats which can be used with these units. The GWT-25, GWT-35, and GWT-50 furnaces do not come with thermostats.
It is also designed for Heritage Cast Iron Stoves DVP-30 and VFP-30.