How old is this windmill?

First off where is the mill located?
Is it on one of Chas's farms proper or someone else's?
Your first link says about his giant country store doing $1M in business in 1945. The lettering on the tail might simply be advertising for the store where it was bought. However since it is steel I would suggest it would be before WWII or after since steel was in demand.

That looks like whats left of the Texas Air National Guard.