Compass dial for latitude 48° 30' North. Round silver fob sundial with a suspension ring for attachment to a fob chain. Convex glass covers both the dial-plate and the compass. The dial-plate is supported by three equidistant radial brass struts. The plate and the compass are both made of white enamel with black enamel markings. On the plate is an hour scale, numbered clockwise 6-12, 1-6, and a shaped brass gnomon. The compass has eight points marked by French initials and a magnetic variation scale, divided anticlockwise from North [0°]-30°. The needle is blued at its North end, with an arrowhead to further indicate North.

The reverse side portrays a painted miniature of the bust of a lady, set under convex glass. The identity of the woman is unknown, but the presence of the painting marks this instrument as a commissioned piece. It is signed 'ROUSSEAU.JNV.FEC.', and was probably made for use in Paris (latitude 48° 52'). A similar item, with a miniature of a nobleman (suggested to be the Comte d' Angevilliers, Suritendant des Batiments de Louis XVI) was in the sale of instruments from the Time Museum of 1988. Both miniatures are of the French school, circa 1765. The similarity of the miniatures raises the possibility that the two instruments were made as a pair.

For more information regarding this dial please refer to the OUP & NMM catalogue, 'Sundials at Greenwich'.