Faber Castell 57/69 Heating slide rule Dutch 1966 Germany

This is a very unusual Faber Castell slide rule special made under Dutch patent and with Dutch text only. It carries the model no. 57/69 where the Dutch name translates to “capacity ruler for local heating” with all sorts of brickwork and other types of wall material, combined with the internal size of a structure. The slider has only scales on the front and extra information on the back and on the back of the slider (also in Dutch). It comes in the original hard plastic case with same text as on the inside of the rule. The rule and cursor are in used condition with clear signs of use and age and so is the case which has some cracks but is still complete. The rule and case measures ca. 30 cm or ca. 12 inches. Check the attached video on how to work your vintage man tool : slide rule operation instructions!