Astronomical compendium for latitude 48° North. This compendium is barrel-shaped. The top of the barrel has a pattern of circular holes and the sides consist of alternating sections of four turned stripes and three plain sections. The top section can be unscrewed to reveal a depression that may once have contained a week calendar. The second section can be unscrewed to a reveal, in its underside, a horizontal dial set over a compass. The compass has a printed and painted compass card with an eight-point rose and all 32 points marked. A glass plate covers all and is held in place by the hour ring of the dial.

Crossing the compass glass are curling supports that hold the shaped brass hinged gnomon, which folds flat when not in use. The third section of the compendium is also removable and contains a magnifying/burning glass. Beneath this, a lunar volvelle, consisting of two brass discs, is set into the remaining body of the instrument. The outer disc has a lunar-age scale and an hour scale. The rotatable brass disc has a pointer, an hour scale and a circular aperture revealing a pictorial display of the phases of the moon. The bottom of the compendium unscrews to reveal a storage space.

Ivory barrel compendia were a fairly common type of instrument, probably made in Nuremberg like the ivory diptychs. The purpose of the storage space in the bottom section is unclear.

For more information regarding this dial please refer to the OUP & NMM catalogue, 'Sundials at Greenwich'.