The Buffalo nickel, which was released by the US Mint in 1913, had a buffalo on one side and a nameless Native American on the other. Due to the hardness of its nickel-copper alloy, it was well-suited for carving. So many Americans worked designs and images into the surface. During the Great Depression, this practiced reached its zenith as unemployed, wandering men carved their own nickels in the hope of selling them for something greater than five cents. The tradition thrived for a generation, and surviving hobo nickels are prized by collectors. Read all about this craft at Appalachian History.
http://www.appalachianhistory.net/2010/04/hobo-nickels-2.html -via Colossal