The instrument is housed in an original box, with compartments carved out of the solid wood. The hinged lid carries the date 1593 and the initials 'V AH' inlaid in ivory, each decorated with a central flower. There is also a later manuscript note in ink: 'Acus Nautica Vetus', incorrectly identifying the instrument as an old mariner's compass. The compass compartment in the base of the box is lined with printed paper.
The compass is 143 mm in diameter and 17 mm thick. It is made up of sandwich layers of ivory (or bone) and wood. The upper face has an outer circular scale  to 24, divided to 1, 1/2 and 1/4, and numbered by 1 in red. The central circle is extensively decorated with flowers and foliage and contains two compasses, with their magnetic meridians aligned with the 12-24 line of the circular scale. Both compass bowls are 26 mm in diameter and carry the initials 'M A' in a scroll.
The underside of the compass has alternating circles of wood and ivory and, incorporated in the outer decorated circle of ivory, the initials 'V A'.
In the centre of the compass is a square hole in which can be inserted one of two plumb-levels that are supplied. Both plumb-levels are in the shape of a shepherd's crook, with a brass bob suspended from the tip of the crook by thread. The departure of the bob from vertical can be measured using a short brass scale inserted through the upright and projecting under the bob. One level is 185 mm long, and its brass scale runs 0 to 15, divided to 5 and 1, and numbered by 5. The shorter level is 103 mm long and its brass scale is divided more roughly and carries no graduation.
Presumably sold by the Milanese dealer E. Imbert, whose label is pasted inside the case lid. Subsequently in the Michel Collection and the Billmeir Collection (accession no. 57-84/134).