This horary quadrant corresponds almost exactly with that described by John Collins in 'The Description and Uses of a Great Universal Quadrant, London, 1658', and John Collins's 'The Sector on a Quadrant' with illustrations engraved by Henry Sutton. The backs of the two instruments are, however, very different and most of the scales on the front of the present example appear on the reverse of the one illustrated in the book. The instrument was described as a sector on the quadrant because the lines along the sides of the front and back can be used as a sector. The front of the instrument carries an astrolabe quadrant and has no hour lines, the hour is read from a scale along the rim of the quadrant. The time is found as follows: once the bead has been rectified, the solar altitude is measured and the string is set so that the bead is on the parallel of altitude, at which point the string will cross the hour scale at the correct time.

The quadrant can be used for all the standard operations that the Gunter quadrant performs, as well as acting as a sector and assisting in the construction of sundials. Similar instruments are in the Whipple Museum (accession number Wh2754) and the MHS Oxford (new inventory number 32551) although both of these are closer to the quadrant described in the Collins text. The MHS also has a quadrant that is identical to the present instrument, in the Orrery collection (new inventory number 25257). Another such quadrant is in a private collection in Belgium.