A fascinating vintage opisometer (also known as a curvimeter or map measurer) designed for accurately measuring distances along curved routes on maps. This practical surveying and navigation instrument would have been used by cartographers, military personnel, hikers, cyclists, and travellers before the widespread use of GPS.
The instrument features a rotating calibrated measuring dial with multiple scales for converting map distances, while the reverse houses a functional compass. It has an attractive ribbed metal handle and wheel at the bottom.