"Ghost signs" are old, hand-painted advertising signs that appear on the side of barns or businesses. Mail Pouch Tobacco was a product advertised on barns and, in this case, the side of one of the downtown buildings in St. Elmo, IL, a community near my hometown. Once in a while you can still spot an old barn along a rural highway that sports a fading Mail Pouch ad. I'll try to find and photograph other examples.
A palimpsest is a manuscript page, on which previous text has been removed and the page is reused for other writing. This ghost sign in St. Elmo has that effect: the Mail Pouch sign is quite legible, but is that "Purina" or some other word behind it? And I see a faint "GO" or "60" above the UC of "pouch", and faint letters above "treat," that might be parts of an older, third sign.