Ring dials are sundials in the form of a ring, with a hole in a movable band to enable the sun's rays to indicate the time on a scale on the inside. They are held in a vertical position with a suspension ring and then correctly orientated.

This is the only surviving ring dial made by the renowned Elizabethan maker Humphrey Cole (died 1591). It is an exceptionally fine example. Not only does it have the essential hour markings and calendrical scales necessary to set it properly, but it can also be used in different latitudes. It also provides useful tables such as the dates of the sun's entry into the zodiacal signs, perpetual calendars, a list of latitudes of cities, a scale for the age of the moon and some astrological information.