This high quality metal double sided circular slide rule was produced by Loga from Switzerland. This model RC comes with the original brown leather sleeve that has kept it in good condition so there are minimal signs of use or age (on side has some small bumps under the surface which you can only see when you look from the side over it. It is fully functioning with a interesting cursor set-ups. The diameter of the slide rule is 12,5 cm or 5 inches. Check the attached video on how to work your vintage man tool : slide rule operation instructions!