Very small ruler, only 6 inch wide.

Rulers like this one are used to plot course lines and bearings on nautical charts. They can be rolled across the chart to the compass rose without changing its orientation.

Catalog: NM.3-15
Date: 1850-1900
WL: 15,5×3,7 cm (6×1,5 in)
Signed: not signed
Origin: England
Condition: in good working condition, smal angle piece missing