The Columbus Dispatch posts this article by Ralph & Terry Kovel about how an old forms of advertising have become a very collectible items:
Vintage advertising, especially tin signs, is being treated like rare folk art by some collectors.
Hundreds of each sign were printed or lithographed on a tin backing and sent to stores to be displayed. The images were sometimes just the brand name or logo, but signs made before the 1920s featured detailed pictures of famous people, sites or colorful pictures of a product.