My 66 has that. It was the standard option heater. Turn the knob to the right for fan speed, there are 3 of them. Pull it out for temperature and the defroster is a handle under the dash passenger side that says "DEFROST" with an arrow pointing up and "ON" next to it.
Personally, I like it since there is only one knob to mess with compared to 3/4 lever setup.
