It reminds me of an ornate piece from a Chinese or Japanese statue from iron. Maybe a piece of the armor on the statue if that is what its from. It does not look like a mechanical component shard or anything like that. Some quick research did not show anything from Civil War era as far as artillery that used a fragmenting charge with that texture. I was hoping that I would find something like that because as stated above it does also resemble a fragmenting grenade piece.