Rieger Merkuria 190 circular slide rule case Norma 1950 Germany

No. This is not an ordinary metal Norma Merkuria 190 but it is a Rieger Merkuria 190. Mr. Böhm was working for the Rieger Company when he invented the Merkuria with 19cm diameter in 1955. It was only in 1959 when he started his own Company called Norma which produced this circular slide rule in large quantities. This early original Rieger Merkuria 190 was the “Commercial” slide rule for the businessman or trader. This one was produced for the Mahle-Kolben Company that produces engine pistons up until today. The slide rule is a complete set with booklet in German and an extra chart in the original sleeve (also marked Mahle-Kolben). Everything is fully functioning and in great condition. The diameter of the slide rule is 19 cm or 7 3/4 inches. Check the attached video on how to work your vintage man tool: circular slide rule operation instructions!