This item is brand new and has never been used. This instrument developed by English Humphrey Cole (1580) is a real lunar calendar that allows measuring the cycle of moon at the given time and assess the level of the tide of the place. The principle developed in the late Middle Ages was used to determine the time at night from the position of the stars.
This calculator handy for seafarers both for fishing access to the ports was very expensive at the time but allowed to ostensibly show the wealth of its owner!