Graphoplex STB Scobey pocket Concrete slide rule pouch 1960 France

This pocket slide rule comes in a STB non signed leather pouch. STB is for the French Concrete Company called Sociëté des Tuyaux Bonna. It was made by Graphoplex from France in the French language  (not signed by Graphoplex) in a special order. The instructions for making calculations on hydraulics in concrete conduits as made by STB. These calculations are based on a formula by Mr. De Scobey. Noticable is the fact that this slide rule originally comes without a cursor so there are not track on the rule sides. Everything is in great condition. It measures 125 cm or 10 inches. Do check the attached video on how to work your vintage man tool : slide rule operation instructions!