Here is a U.S. Navy submarine clock.  It shows it was made by the Chelsea Clock Co., Boston and U.S. Government lower on the face.   There is a glass cover over the face and a hole near the #6 for winding - but I do not have a key for winding and am unsure if it operates. The face measures about 6 1/2 inches in diameter and the back is about 7 1/2 inches in diameter.   The case feels like a very heavy hard plastic.  It shows some light wear on the black finish and some old adhesive on the back.   Please see the pictures and ask any questions.  

Thank you for looking.  (Inv 26,007)