I do not know about earlier years, but the exterior windshield visor was
a GM accessory for 1954 Chevrolet trucks. There is no exterior sunvisor listed in the 1947 Chevrolet Truck Data Book
Fulton also sold an aftermarket sunvisor that had a divider in the middle. GMC trucks also had an GM exterior sunvisor in 1954 but I think it had slightly different mounting brackets than the one for Chevrolet trucks.
The
1951 Chevrolet Accessories Manual shows an exterior sunvisor for a car but no mention about one for a truck.
Tim