This folding compass and dial was made in Germany (Nuremberg) in 1562 and is attributed to Georg Hartmann (1489-1664). The outside of the compass is engraved with a dial and a table of latitutes, while the interior is engraved with various calculating diagrams containing a compass, sunk under glass, the needle of which is missing.
Hartmann was active in Nuremberg from 1518 onwards. He apparently provided the technical designs for sundials, as shown by different engravings depicting diptychs produced by him, signed and dated between 1535 and 1553. Sundials were portable and essential for accurate time-keeping, and would have beed used by merchants, sea captains, travellers, and indeed anyone who wished to know the time, in the days before accurate pocket watches or of course wrist watches. They relied on measuring the sun’s changing direction in the sky, indicating the hour of the day through the angle of the shadow cast by the gnomon, which was the string in the hinged portable sundials. In order to work correctly the direction dials das to be properly aligned, and for this reason such portaqble sundials needed to incorporate magnetic compasses.
Ivory was a suitable material for a number of reasons: it was not heavy, did not warp as easily as wood, and its light colour and realtive softness meant that it was easy to inscribe. Such objects were produced from the fifteenth century up to the early twentieth.