This wonderful device was used to solve problems concerning the calendar, tide tables, the rising and setting of the sun, moon, or stars, and the positions of planets. This example consists of three parts: an engraved circular calendar, inside of which is mounted a separate movable paper disc (engraved with the zodiac sign Virgo), and finally a rotating pointer or Index mounted at center with a red satin ribbon. These were included in scientific books and atlases and because of their delicate nature most have not survived in tact.