2 5/8″ high x 2 1/8″ wide x 1/2″ deep. All iron. Double bitted post key. “F. W. MIX” is stamped on the obverse of the body. “US MAIL” is stamped on the obverse of the shackle. “NO.”↔”3” is stamped on the obverse of the shackle. “US MAIL” is stamped on the obverse of the key at 12 o’clock. “F. W. MIX” is stamped on the obverse of the key at 6 o’clock. “3” is stamped on the reverse of the key.