This is a WWI dog tag, one of the earliest ones. During the US Civil War, in the 1860s, the soldiers realized they may not come back from the battlefield, nor would they be recognizable. So they began to attach papers and cards inside their uniforms, usually in the back, with their names on them and addresses… just in case. Clara Barton made it part of her life’s mission to document them and notify families. Along with founding the Red Cross… So by the next Big War(WWI), Dog Tags were available to the men. They don’t look like they rectangle ones we’re familiar with, but they beat paper notes. Taken last fall in Pine Bluff, Ark USA at their train museum, with a SanyoVPC-E2100.