If you are overly concerned about mold, then buying a Vintage trailer is not for you. It goes with the territory and takes a while to get under control.
That being said, the upper pic looks like a Vista-View window. These are notorious for leaking, having leaks past the outer glass, the UV film inside peeling and retaining moisture.
There are numerous threads on the subject. Most deal with breaking the inner pane, cleaning and resealing the outer frame and glass.
The lower pic looks like an opening side window. These also have a plastic film on the inner surface of the glass. Being in Canada I might guess this trailer has the storm window option which could trap moisture as well. Some of the window film on my trailer had peeled and become cloudy. I have striped the worst ones off.
If it is indeed mold, it would be easy to check after opening the window.
You didn't state the size of the trailer. The '70s era trailers have a problem with water soaking into the rear of body causing floor rot and frame damage. When you inspect the trailer make sure to check for soft floors in the rear and by the door.
Welcome to the Forum. Good Luck. I hope this hasn't scared you off from buying an Airstream. Just trying to let you know what you might be getting into.
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