Astronomical compendium for latitude 51° North. This ivory compendium is barrel-shaped. The top and bottom of the barrel are engraved with circular designs and inlaid with coloured paste. The top section can be unscrewed to reveal a brass day indicator, and the second section can be unscrewed to a reveal, in its underside, a horizontal dial set over a compass. The brass compass has a 16-point rose and the needle is missing. A glass plate covers all and is held in place by the hour ring of the dial.