Fearns Tank capacity Calculator full set circular slide rule 1960 England

This unusual high quality 5 layer and 2 sides slide rule was produced by Fearns Calculators from England. Made ca. 1960 specifically for calculating the capacity of huge cylindrical, ellipsoidal, spherical and rectangular tanks.It used both sides with see-through sliders making calculation on multiple scales possible. There is an instruction leaflet in English in addition to the short instructions on both sides. It comes with the original signed brown sleeve that has kept it in great condition so there are minimal signs of use or age. It is fully functioning and the diameter of the slide rule is 19 cm or 7 1/2 inches. Check the attached video on how to work your vintage man tool: circular slide rule operation instructions!