I have always been fascinated with the recycled material that can be found inside cars. I did an article for CTT magazine in the 1990's called "Deep Dark Secrets of Louis Marx" about the litho inside 556 cabooses, which turned out to be surplus back-drop litho from a pre-WWII Marx shooting-gallery toy. I will go into that another time, another place.
Here is some interesting surplus litho found inside 1930's 4 wheel AF cars and some paint can litho found inside a Hafner Sunshine Special car.
Note the 1933 Century of Progress trolley litho