The Keuffel & Esser K&E N4081-3 Log Log Duplex Decitrig Slide Rule is a high-quality mathematical instrument made in the United States. This slide rule features a duplex design, allowing for precise calculations in both directions. It comes with a protective case for easy storage and transport. Ideal for students, engineers, and mathematicians, this vintage tool offers a reliable method for solving complex equations without the need for a calculator.