Vintage Keuffel & Esser K&E Log Duplex Decitrig Slide Rule 4081-3 Leather Case Vintage Keuffel & Esser Co. Log Log Duplex Decitrig slide rule, model 4081-3, crafted in the USA. This precision instrument features a double-sided design with a clear cursor and comes housed in its original brown leather protective case. A classic piece of engineering history, it showcases the intricate scales used for complex mathematical calculations before the digital age. The leather case shows a rich patina and includes the embossed K&E logo on the end cap. #Retro