Tom, If you owned a 61 beetle, these levers were round knobs in your earlier beetle. One controls the flappers on the heater boxes, where heat from the engine exhaust manifold is exchanged with fresh air feed by the the cooling fan. Basically, your temp control lever.
The other lever or knob controls flappers under the rear seat that would direct heat either from under the seat or through the heater channels to front cabin, usually defrost only. While air cooled vw’s didn’t heat real well when idle, at driving speed, a good set of heater boxes can toast you right out of the car and since the temp control lever work you basic flap over the hole, I find myself tuning on and tuning off the heat in my 72 beetle to try and regulate the temp somewhat.