Thats Pretty cool..It looks like a Small Sundial, that is missing the center piece, the back looks like it was mounted to something at one time...I looked at some sundials, and didnt see this stlye..but i did notice they use stars on alot ....good luck
Not a sundial - the numbers on the face of a sundial don't go in a full circle (check it out if you don't believe me - the sun would have to never set for that to work).
Much too small to be a clock face. Perhaps an alarm setting. It could possibly be in a clock face behind a small window allowing the Roman Numeral to show through the opening.