The instrument consists of a quadrant with two long pivoted arms, one fixed and the other movable.
The obverse is laid out as an horary quadrant labelled 'Horae Ante' / 'Post Meridiem' with hour lines 6 to 12 to 6, numbered by 1 and divided to 1/4 hours. Further to the outside is a non-linear declination scale 0 to 90, numbered by 10 and divided to 5 and 1. It is labelled 'Declinatio Arc<us> diurni et Nocturni Horarum 14 et Horarum 10'. Adjacent to this scale is a scale of solar declination labelled 'Zodiacus' extending over 231/2?, marked with the symbols of the zodiacal signs, each pair with a degree scale 0 to 30, numbered by 10 and divided to 2. Along the arc is a transversal degree scale 0 to 90, numbered by 10 and divided to 5 and 1. Between this scale and the declination scale are inscribed the signature and date 'E. Habermel 92'. Both arms bear degree scales 0 to 90 (numbered by 10 and divided to 5 and 1) closer to the centre and scales 0 to 60 (numbered by 10 and divided to 5 and 1) further to the tips.
This side of the instrument is used for laying out sundials for a particular latitude. The latitudes are indicated on the 0 to 90 degree scale on the movable arm. The arm is moved over the horary quadrant, and where the appropriate latitude intersects with a particular hour line the corresponding angles can be read off on the transversal scale. The scale 0 to 60 on the arms correspond to the transversal scale on the quadrant. The zodiacal scale indicates the solar declination as a function of the solar longitude.
The reverse of the quadrant is laid out as an horary quadrant with markings for morning and afternoon hours 6 to 12 to 6, numbered by 1 and divided to 20 minutes, and labelled 'Horae Post' / 'Ante Meridiem'. Inside this quadrant is one quarter of a Rojas projection with hour lines 12 to 24 marked twice across the quadrant and once along the horizontal edge. They are numbered by 1 and divided to 1/2 hours and along the edge further to 1/4 hours by alternate shading.
Along the arc is a degree scale 0 to 90, numbered by 10 and divided to 5 and 1. Between this scale and the horary quadrant markings is a scale of solar declination labelled 'Zodiacus' and extending over 231/2?, marked with the symbols of the zodiacal signs, each pair with a degree scale 0 to 30, numbered by 10 and divided to 2.
The arms have identical non-linear degree scales 0 to 90, numbered by 10 and divided to 5 and 1.
The fixed arm has one hole, the movable arm has two holes close to the tips. It is likely that these holes were for sights or an arc with a fixing mechanism to keep the movable arm at a particular place.
This side of the instrument can be used for determining the maximum length of daylight at any latitude and any time of the year. For this purpose the movable arm is set along the zodiacal scale for the correct time of the year. The intersection of the appropriate latitude on this arm with the hour curves 12 to 24 on the quadrant indicates the length of daylight.
The instrument is decorated with a geometrical pattern.
The instrument was presented by A.W. Franks in 1867 and is described in F. A. B. Ward, A Catalogue of European Scientific Instruments in the Department of Medieval and Later Antiquities of the British Museum (London, 1981), p. 94, no. 273.