Dipleidoscope dial for latitude 52° North. It has a square base set on three small feet, one of which is also a levelling screw. A rusty steel compass needle is set in a glazed rectangular box along one edge. The needle can be locked in position by an arm operated by a lever on the side of the box. This box has a degree scale at one end, divided anticlockwise [0°]-[40°]. The fact that 20° is in the middle might suggest that this was the magnetic variation at the time of production. There is also a bubble level on the base.

The semicircular hour arc is inclined at an angle to the base. It is numbered clockwise IX-XII, I-III. An inclined brass pillar set at the centre of the hour arc supports the prism and mirror attachment and can be turned and locked in position. The attachment consists of a squat cylinder, in the upper face of which is a blue glass aperture behind which are set two mirrors. The number '1577' is scratched on the underside of the base; this is probably the serial number of the instrument. Such a serial number suggests that it was made in the 1850s, since an earlier number appears on AST0235, which must have been made between 1853 and 1860. 'E I DENT PATENTEE LONDON' is stamped on the hour arc.

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