M.H. Mear Fearns pipe flow calculator circular slide rule 1960 England Holland

Large and high quality heavy plastic slide rule was produced is called the “Pipe Flow Calcualtor” and build according to the copyright by M/H/ Mears & Co by Fearns Calculators from England (not signed). Made for a Dutch company called “Jiskoot Automation N.V. It features at least 10 different scales to be read with cursor or from a window. Made ca. 1960 specifically for liquids and gasses that flow through pipes with calculations on gravity, viscosity, velocity, pressure, etc for different pipe diameters aiming at a streamlined flow. On both sides there are also instructions for use. There is no sleeve but the slide rule is in great condition with minimal signs of use or age. It is fully functioning and the diameter of the slide rule is 19 cm or 7 3/4 inches. Check the attached video on how to work your vintage man tool: slide rule operation instructions!