To my knowledge, there was no one-piece Airstream manual for the '50s models of AS trailers.
What you got was a collection of manuals put out by the sub-suppliers, such as the water heater, cooktop, oven, and so on.
Did you snoop around on the service department's section of the Airstream.com website? They are always adding things for the vintage trailers, it seems.
Plus folks on here can be a great source,of course. Ask and you will receive.