This circular horizontal sun and moondial has a compass box with mica cover and brass lid attached to the handle, decorated on the outer side with strapwork.
One of the faces is engraved on the limb with hours from 4 to 12 to 8, divided to the half hours. A folding and decorated gnomon for latitude c. 48? is hinged on the lunar volvelle. This is engraved 'OMNIA ? CVM ? TEMPORE ? PRETEREVNT', and with hours marked from 4 to  to 8, divided to the quarter hour with alternate shading. The volvelle is pierced twice, with a small aperture indicating the moon's age in figures and a bigger one showing the phase visually. The remaining central part of the volvelle is decorated with strapwork.
The other side of the dial has a nocturnal with handle at 15 October. On the limb is a degree scale, divided by ten days, subdivided to two, numbered by ten. Further to the centre are the zodiac symbols, then the calendar scale, divided to ten days, subdivided to five, to two, numbered by ten to 30 or 31 as appropriate. The equinoxes are at 13 march and 15 September. Further to the centre are the initials of the names of the months in Italian or Latin, then the rotating arm of the nocturnal, with hours indicated 1 to 12 twice, then the arm of the nocturnal, both decorated with strapwork engraving.
The instrument was presented by A.W. Franks in 1871, 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.27, no. 41.