The tinted front window is as you said in the first part of your post.
"Most front windows look like they have a tinted window cover on them from the pictures."
It is known as a "Rock guard" to keep the front window from being shattered when your tow vehicle kicks up a stone or something.
They were / are standard equipment, but as the trailers age or are neglected they become broken or are just simply removed. They can be had through most Airstream dealers.
AIR#3788 TAC IL-10