I am pleasantly surprised to have enough energy this morning to do some posting. (Relentless insomnia, month after month, is wrecking my sleep... and you know what that does.) Your find is one of the many variations of patriotic Militia "panel-plates" shown is the book "American Military Belt Plates" by O'Donnell and Campbell. And, Antiquarian's estimate is correct, it is from the mid-1800s (a.k.a. the "mid-19th-Century").