A late 17-Century Dieppe ivory diptych dial, unsigned, the surfaces with incised decoration, the inner lid with spring loaded string gnomon and sliding latitude bar reading over a 40°-50° scale with additional levelling arrow plummet and decorated in gilt over a blue ground with the names and latitudes of twelve Continental cities and towns. The panel surrounded with painted scroll decoration in red. The horizontal dial arranged for latitudes 42°, 45° and 48°, the compass card with blued iron needle and gilt decorated compass rose (possibly later), the dial with three brass hooks and eyes - 2 5/8in. (6.7cm.) long.