These small tools are very handy when studying a (road) map. Rolling the small wheel over the map, handling this instrument like a pen, will make the hand move over the dial. When you start the hand on top / zero you then select the correct side with the requiered scale / ratio you can read the exact amount of kilometers in real life. Nice versions from ca. 1950-1980, 3 colorful double sides ones from Germany and one single sided marked E.H. from Switzerland. They are working condition with signs of use and age, 2 come with the original box. They measures ca. 7 cm or 2 3/4 inches high. Check the video for a vintage desk stuff collection!
