S. MAIL” – “1877”. 2 7/8″ high x 2 1/16″ wide x 7/16″ deep. Steel body. Steel shackle. Brass pins. Lever. Post key. “UNITED STATES MAIL LOCK PAT’D JAN 20.1891” is stamped on the obverse of the body. “U.S. MAIL” is stamped on the obverse of the shackle. “MADE IN U.S.A. 1877” is stamped on the reverse of the shackle. There are no stars stamped on the obverse of the case at 11 o’clock. “US” is stamped on the obverse of the key. Frank W. Mix Patent # 445121.