I found this today on a farm field where a Civil War battle took place. It is made of cast brass, tapers at the end and has the square "tab" on the other end. Diameter is about 3/4" at thickest part. Ideas? It just has a blunt end, does not appear to be broken on the round part. There is no curvature to it. Of course it could be 20 years old too, but unlikely with that patina.