The instrument consists of a box with a fixed suspension ring surmounted by a hinged brass lid serving as the hour plate.
The cover leaf has a central hole through which the (missing) gnomon would have been inserted; it is accompanied by two smaller holes. Fitting flush with the leaf is a folding arm used to set the elevation of the plate.
The outer face has a circular scale of hours 1 to 12, 1 to 12. Within this scale there is room for a rotating disc, now missing. Above the midday point of the hour scale is a small cartouche bearing the date '1598'. In the four corners of the plate winged heads.
The inner face of the cover leaf carries the inscription 'NON . SIBI . SOLI . VIVERE . SED . ET . ALIIS . PROFICERE . VVLT' and engraved figures of St Francis of Assisi and St Anthony of Padua.
The main box carried the instrument's compass, which is now also missing. The compass bowl is 35 mm in diameter and surrounded by foliate engraving through which a hare, a boar and two dogs are running. To the side is the scale of latitude from 20 to 60?, with notches at every second degree. The co-latitudes are also marked from 70 to 30?.
The appropriate sides of the box are marked 'ORIENS', 'MERIDIES' and 'OCCIDENS' within decorative panels.
The base of the box carries the signature 'F. Hieronimus de Arresse' above a table of the latitudes of 24 Spanish and Portuguese towns.
Provenance: Lewis Evans Collection S. 8.