Only the brass case and lid remain of this astronomical compendium. The outside of the lid is engraved with concentric rings, the first four used to calculate the date of Easter, as follows: 'Leap Yare', Dominical Letters 'Do<m>inica let', Golden Number 'Gould nu<m>b', and a table of epacts 'Epacte'. The central rings are used to calculate the day when the sun enters a particular zodiacal sign, as follows: 'Moneths' and the initials of the names of the months, 'Daies' and the day, 'Sunne' and a ring of symbols for the sun, 'Signe' and the symbols of the zodiacal signs. The spandrels space is decorated with foliage.
The inside of the lid has a quartered shield, with the arms of Stanhope, Mauleval, Longvilers, Lexington.
The outside of the box is engraved with similar rings, with the Prime Numbers labelled 'The Prime', the Dominical Letter labelled 'Sonda lette', Quadragesima labelled 'Fir lent Son', and Easter day labelled 'Easter dom<inic>a'. In the spandrel spaces is foliate decoration.
The inside of the box is empty.
The instrument has a ring for suspension.
The instrument was presented by A.W. Franks in 1886 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.127, no. 364.