A Swiss Kern Aarau kippregel surveying instrument. The instrument is made of brass and aluminum. Marked, Kern, and numbered, 21707. Circa: the first half of the 20th century. Kern Aarau was a Swiss manufacturer of precision instruments, including surveying equipment, telescopes, and binoculars. The company was founded in the mid 19th century by Jakob Kern in the town of Aarau, Switzerland. Kern Aarau became known for producing high quality instruments that were popular with surveyors, engineers, and other professionals who required precise and accurate measurements. Antique and Vintage European Survey and Optical Instruments and Tools For Collectors.