This dedicated slide rule chart was developed specially for calculation gas and cyclones developed for and by the Büttner company from Krefeld Germany. It was produced by IWA with number 515.11 in the late 1960’s. The original blueish sleeve also has the Company logo on it. Instructions are on the rule itself. The slide rule is in good condition with small signs of use only. It measures ca 22 cm or ca. 11 inches long. Check the attached video on how to work your vintage man tool: slide rule operation instructions!
