Hi,Welcome to Just Answer, My name isXXXXX will be helping you with your appliance issue today.
on the back of the thermostat itself there is a part # XXXXX if you can get that # XXXXX can cross reference this, also find out how many wires are running to it, this is the only way without a model #. the tech should have checked the thermostat itself for the #. I would call him back and ask him to check the thermostat itself for the part #. hope this helps, thanks, Bryan