Vintage Faber-Castell 1/87 System Rietz slide rule, Germany 40s

Good condition.

Primary purpose

This is an analog calculating device used by engineers, scientists, and students before the widespread adoption of electronic calculators.

What you can do with it

Multiply and divide numbers. Square and extract square roots. Find cubes and cube roots. Calculate trigonometric functions (sines, tangents). Calculate logarithms and perform operations with constants (e.g., pi).

How it works

It operates on the principle of adding and subtracting logarithms. The slide rule consists of a fixed body, a movable slider in the center, and a transparent slider with a target line (not pictured). By moving the scales relative to each other, segments proportional to the logarithms of the numbers are added, allowing you to instantly obtain the result of a multiplication or division.