Graphoplex CTN metal tubes pocket slide rule 1960 France

This slide rule has been specially constructed for CTN, the Compagnie des Tubes de Normandie by Graphoplex. It has the French language on the back as well as an additional instruction card in French also.  The front has scales for standard calculating as well as several additional scales for calculating metal tube constructions. On the back of the slider there are additional scales as well. It is branded CTN on the back of the slide rules and also comes in the original CTN signed leather sleeve. The interesting dedicated curser, rule and sleeve are complete and in very good condition. with minimal signs of use and age. It measures ca 15 cm or 6 inches. Do check the attached video on how to work your vintage man tool : slide rule operation instructions!