Spherical equinoctial dial for latitude circa 51° North. A turned plaster pillar (which is very chipped) supports a spherical plaster ball. There is a cylindrical hole in the underside of the base where the dial was once fixed to a plinth. The dial ball has two stars at the top and bottom of the axis, which are partially coloured yellow. The hour-lines radiate out from the top of the axis and they are marked from 5 am to 7 pm. The hours are numbered on an equatorial yellow band V-XII, I-VII and beneath this band there is further decoration. The gnomon is provided by a metal semi-annular ring fixed to the two ends of the axis and it is free to rotate. Over the Equator there is a broken projecting triangle. The instrument is signed '1767 BERT'.

Bert is only known through this instrument and another in the NMM collection (AST0174). The time can be found either by marking the edge of the shadow of the globe in the hour-circle, or by turning the semi-annular ring until it casts no shadow, at which point it will be over the correct time.

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