I have the same thermostat. Apparently this is not the model number. From the Honeywell web site: To find the model number on the thermostat, place your four fingers on top of the thermostat, and your thumb on the bottom. Pull from the bottom towards yourself to remove the thermostat. Use both hands if necessary. The thermostat will be in your hand. Look at the back of the thermostat. In the upper left hand corner of the thermostat, there will be a model number starting with a T or a CT.