Aristo stahlbeton 939 n=15 Göttsch concrete slide rule case 1960 Germany

This earlier slide rule and container are made by Aristo from Germany. This model is the 939 Stahlbeton Duplex, with n=15 cursor. It has special scales on both sides as well as a spectacular cursor. Used for calculations for reinforced concrete according to the Göttsch system. Everything is complete and in good condition but with signs of use and age which is mostly the bleeding of the ink as shown in the pictures (priced accordingly). It also comes with its data sheet. It measures 33,5  cm or 13 1/4 inches. I also have full set later version n=15/35 for sale. Check the attached video on how to work your vintage man tool : slide rule operation instructions!