KNM duplex circular slide rule full set 1960 Holland

This rare double side slide rule has comes in Dutch and English and was probably produced  by ALRO from Holland, ca. 1960. It is specifically made for calculating friction in pipes, capacity and power efficiency for the work of the Royal Dutch Engineering Works or KNM (Koninklijke Nederlandse Machinefabriek) aka Begemann from Helmond in Holland.  It comes with the original sleeve that has kept it in great condition so there are only small signs of use or age from normal use. It is fully functioning with all parts intact. The diameter of the slide rule is ca .12 cm or ca. 5 inches in diameter. The original manual is in Dutch. Check the attached video on how to work your vintage man tool : slide rule operation instructions!