Object Name: ring dial
Dimensions: 5.9 x 1.1 x 5.4 cm (2 5/16 x 7/16 x 2 1/8 in.)
Description: This brass ring dial has two pin holes in a sliding circular ring that runs in a central track. The ring is moved by a knob and is used to position the holes for the correct season.
The solar declination scale is divided into 10-day intervals and marked by the initials of the months. The winter half of the year is on one side of the suspension ring; the summer half is on the other side. The are marked "W" and "S" respectively. The vernal equinox is set to March 10.
There are two interior hour scales. Hour lines for the summer months are marked 4-12-8 and cross three vertical calendar lines. Hour lines for the winter months are marked 6-12-5, and also cross three vertical calendar lines.
There are initials on the lines between the summer and winter dials: "S H W"
Mathematical measurements show that the dial is made for the latitude of 52°.
Signed: inside ring: S H W
Function: The ring dial, or poke, finds the hour by means of the sun's altitude corrected for the seasonal declination.
Curatorial Remarks: Christie's DC830/99 7175 engraved "SW" 7128 engraved"SHW"