Is the Air Vent WCGB gable-mount power fan wiring made of copper?

Yes, the wiring on the WCGB motor, as well as all other Air Vent power vent motors, is comprised of copper windings and copper leads.

Yes, the wiring on the WCGB motor, as well as all other Air Vent power vent motors, is comprised of copper windings and copper leads. The leads in the thermostat and humidistat controls may have a silver appearance (similar to aluminum wire), but these are copper wires that have been tinned for soldering purposes.