You are most likely referring to the Fresh Air Heater (as apposed to Recirculating Heater).
When you list this in the Swap Meet, you should provide links to photos (so it is clear what you are selling). Also indicate (and show photos) if it includes a working control valve, control rod and mounting bracket, defroster cable/knob/bracket, and motor switch. If you have used the heater and the core does not leak, you might want to state that.
