You do have the heaters mixed up.
The Recirculating Heater (and defroster) was supposedly the same for all Advance-Design years.
There was no defroster manual "control arm" on the "Air-Flow"/"Fresh Air" (de luxe) heaters until 1953-55. The earlier Advance-Design "Air-Flow"/"Fresh Air" heaters had a cable-controlled defroster "arm".
What type/style of heater and year of heater are you referring-to, Deve?
The decal you show has different defrost labels for different types of heaters, recirculating and "deluxe".
1947-1955st GM truck heater decals
