The compass is housed in a wooden box, with a lid and an internal glass cover to allow the compass to be viewed while in the box. It is a dry card compass, marked with the points but not with degrees. The brass compass-housing fits onto a spike in the bottom of the box that allows the compass to move around and remain level. When not in use, a wooden slide within the box holds the compass in place.

At the north point of the compass card is the inscription ‘G. Knight Invt.’. This refers to Dr Gowin Knight (1713–72), who in 1745 invented a method for making strongly magnetic steel bars, and from this developed a steel compass needle which retained its magnetism much longer than the needles used previously. This innovation did away with the need to continuously re-magnetize compass needles with a lodestone during a voyage, although compasses were taken to an instrument-making firm to re-magnetize the needles once they returned to port.

The maker’s name appears both on the compass card and on the cover of the compass and refers to George Adams (1750–1795) of the Adams firm founded by his father. The firm was one of the leading instrument suppliers in London in the late 18th century, with clients including the Board of Ordnance as well as being appointed instrument makers to the king. George Adams was employed as the sole agent for Knight’s compasses.