This is a dedicated version (n=10) concrete slide rule by Nestler from Germany. It has the model number 0439 (where 0438 would be the system Jakob n=15). This slide rule is for calculation of concrete mixtures including reformed with iron bars, per the system Jakob (n=10). It has a special scale on the front as well as on both small sides and a multi sided cursor to match It has the original leather sleeve with Nestler name (and ITS logo) as well as the original out box. It is all complete and in close to unused condition. It measures ca. 30 cm or 12 inches long. Do check the video below on how to work your vintage man tool : slide rule operation instructions!
