Welcome to the Forums and the world of Vintage Airstream ownership!
Your windows are definitely different from those in my 64 Over lander. They look more like those that I have seen in 1965
Airstreams. There are numerous possibilities such as the coach being a very late 1964
production or an early 1965
delivered and titled in 1964
Good luck with your investigation!
P.S. -- A big difference between 1964
would be the entrance door -- a 64 would have a door-within-a-door while a 65 would have a solid door with separate screen door.