I believe it is made of either copper or brass. It is very brittle now that it has been in the ground so long. It is not painted, I scratched the patina off of it getting it out of the ground. It was almost a foot deep. I almost gave up on it. I am leaning towards part of a sash buckle. Am interested in knowing if the 25 regiment may have had such sash buckles on their uniforms. Maybe not military at all. Thanks for looking