Large well know slide rule that was made in Germany by A.W. Faber & Castell and is called the Castell Novo Duplex 2/83N. This one comes with box, instructions in German. Both slide rule and slider are invert good condition with hardly any yellowing between the lines. The box is complete and in working condition, (no cracks). It measures ca. 38 cm or 15 inches long. This great rule is reinforced with metal pieces on the ends and ribs on the ends of the slider. Check the attached video on how to work your vintage man tool : slide rule operation instructions!