An antique brass universal equinoctial ring dial. The dial consists of two rings and a bridging bar inside the outer ring. The outer ring is known as the meridian ring represents a circle through the North and South celestial poles. The inner hinged ring represents the celestial equator and is engraved with a double twelve hour scale. The rotating bridging bar engraved with a calendar for the day of the month is set at the poles of the meridian to represent the axis of the world and a slider with a pinhole is set between the bars of the bridge to act as the shadow marker. Circa: the late 18th century. Antique Astronomical Instruments For Collectors.