Sorry to be the bearer of bad news, Grim, but this is a fantasy belt plate dating from the 1960's or 70's. It's listed in Kerksis' Plates and Buckles of the American Military, 1795-1894 as "an imposition made in England for the tourist trade." It also appears in Crouch's Repro Buckles of the Civil War, with comments clearly indicating that it is neither an authentic Civil War item nor a replica of one, but a modern concoction.