This instrument consists of a perpetual lunar calendar on one side and an abacus or tide calculator on the other. It is based on the need to to predict the time of the passage of the Tides and the intimate relationship of these with the influence of the rotation of the Moon in its orbit around the Earth.

Knowing the phases of the moon is of great cultural importance for many peoples: calendars, religious festivals, agricultural practices, etc. The tide calculator or abacus is used to calculate tide times because of its important effects on navigation, ports and fishing.      (H 38).

Measurements:

Maximum Height: 16,2cm / Diameter: 12cm / Thickness: 0,7cm