Compass dial for latitude 51° North. Round brass compass dial with a screw-on lid. The cutaway dial-plate bears Roman numerals for use with the folding gnomon as a horizontal sundial. Inside the base under the glass cover is a printed compass card, showing the cardinal and quadrantal points of the compass, with a fleur-de-lys at the North point. It has a steel compass needle. Inside the lid is pasted a printed compass rose showing 32 points of the compass.

The standard of engraving on this instrument is not very high, suggesting that the dial was made by an amateur. The latitude corresponds to places in Southern England. The dial could possibly have been intended for use in London (51° 32').

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