Slide rules were used mostly for multiplication nd division, not for measuring lengths.
Each number to be multiplied or divided was represented by a length on a slide rule which had a logarithmic (non-linear) scale. The numbers were aligned on the slide ruler to read the sum of the logarithm and then calculate the two numbers.
CreatorNestler BrandProvenance and SignifcanceThis pocket slide ruler was owned by Franz (Frank) Behrens of Shellharbour.