Pocket dial comprising a small folding gnomon in brass, mounted on a small brass ring 4 cm in diameter and contained in a small ivory sphere, which acts as case for the instrument. The outer surface of the case is ornamented with black decorations, representing the zodiac with the zodiac signs and names of the months in French, the tropics, the polar circles, and the equinoctial and solstitial colures.
A.J. Turner ed. (1990).