Aristo stahlbeton 939 n=15/35 Göttsch concrete slide rule full set 1970 Germany

The production stamp 2LA3 put this one in 1970, so a later edition (elaborate cursor and rubber inserts in the feet) and it is still a complete set. It contains the outer box with 939 number, the slide rule, plastic container with sheet and the manual in French. This model is the 939 Stahlbeton Duplex, with large n=15/35 cursor. It has special scales on front that work together with the cursor and there are some caluculation to be made on the back as well. Used for calculations for reinforced concrete according to the Göttsch system. Everything is complete (rubber feet are good) and in very good condition, with only very small signs of use and age (mostly to the box that is missing one small side). It measures 33,5  cm or 13 1/4 inches. Check the attached video on how to work your vintage man tool : slide rule operation instructions!