Mechanical equinoctial dial for latitude 46° North. The brass base-plate is shaped like an artist's palate and supported by three turned brass screws. The hour-plate support is set on a brass strip along the meridian line. The circular, hinged hour-plate is toothed and has a brass pointer pivoted at its centre. This carries a minute-dial at its other end. A semicircular ring is set perpendicular to the minute-dial across the latter's diameter. It is spanned by a bar parallel to the minute-dial. Both this bar and the semicircle have pinhole sights in the centre. These allow the sun to fall on a vertical line drawn on a shaped brass plate perpendicular to the pointer arm.

The simplicity of the design and the style of the numerals on the minute-dial point to an English origin for this instrument, although the latitude (46° North) indicates that it was probably used in France. There is no alidade. Instead, the index is turned until the pinhole sights set over the minute-dial allow the sunlight to fall on the vertical line drawn on the shaped brass plate set further down the index arm. There is no need for an adjustment for declination because the sun will always fall on the inscribed vertical line when the index arm is correctly oriented.

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