17th century signed Italian parallel ruler

A 17th century Italian parallel ruler, used to plot courses and directions on a nautical chart. The ruler bears different signatures: ‘Pex, Geometric’, ‘Fecit Palumb,’, ‘Anno 1643’ and ‘Palmus Genuen’. Which indicate that is made by Palumb in 1643 and depicting the palm of Genua.The Parallel ruler is connected by four screws, On the left plate there is an arrow pointed to a dot. And on the right there are on both sides three dots. The ruler contains 9 rows and goes to 900 in length.Length 53,56 cm width: 5,7 cm.