Non Dug Civil War New York State Artillery Horstmann RMDC Backmarked Coat Button

Non dug Civil War gilt brass New York State Artillery coat button. The front has a centered eagle & shield with EXCELSIOR above and N.Y.S.A. NATIONAL GUARD below. The reverse has an RMDC Horstmann Bros. & Allien backmark. The shank is straight. It measures 20 mm's in diameter. $75