[Instrument on the left hand side of the image]

Combined nocturnal, sundial and lunar volvelle.

Obverse
Nocturnal with a bracket and suspension ring on urn-shaped mount, which also holds a compass. Rotatable ring rather than disc.

The main disc has an outer zodiac scale divided into 30 days per month with chequerboard divisions every 2 days.The smaller calendar scale for the nocturnal has the months labelled with capital letters, subdivided into units of 10,20,30 and smaller units of 2 days. Index arm is labelled 'ligne de foy [French: the line you can trust] with a decorated disc at end of arm.

Reverse
Sundial and lunar volvelle with two rotatable discs and a compass set in mount of suspension ring.

Compass is brass, marked with cardinal points and a glass cover.
Main disc: Hour scale clockwise divided to 15 mins.
Lower rotatable disc: Hour scale clockwise divided to 30 mins. Lunar-age scale anticlockwise divided to half a day.
Upper rotatable disc with pointer: Hour scale 1 - 12; aspectarium in centre. Central aperture to reveal phases of Moon pictured at quarters.

The gnomon of the sundial is missing.