This round radiation slider rule is from the cold war era and comes in it’s complete manual booklet that also functions as a case. The slide rule itself was made by Nestler for the Company “Total KG. Foerstner”, also from Germany somewhere in the 1960’s. It seems to have been in use for a long time since it comes complete with a set of instructions in Dutch from the Nederlandse Spoorwegen (the Dutch railroads) from 1984. The manual and slide rule are in great condition, hardly any signs of use or age and fully functioning. Diameter of the disk is ca. 10 cm or 4 inches, about the same height as the manual. Do check the video on how to work your vintage man tool : slide rule operation instructions!