2x Alro duplex circular slide rules for machinery 1960 Holland

These double side slide rule were produced  by ALRO from Holland, ca. 1960. One is for Dutch company E.M.F. Dort and calculates copper cables resistance on one side and axel power for engines on the other side. It has instruction in Dutch on the rule itself. The other one is a grinding calculator with instructions booklet in Dutch for the Dutch Cincinnati Milacron N.V. company. Both come with the original sleeve that has kept them in great condition so there are only minimal signs of use or age. It is fully functioning with all parts intact. The diameter of the slide rules is ca .12 cm or ca. 5 inches in diameter. Check the attached video on how to work your vintage man tool : slide rule operation instructions!