IWA 0594 Psychrometer humidity slide rule 1960 Germany

This is a very specific slide rule for calculating air humidity moist and related temperatures. It was made by IWA, designation 05.94 from Germany for the Karl Weiss company, ca. 1960 (the 1970’s version has a black rim). It has a great and white color scheme and a double cursors with hairlines on both sides. It is in complete and working with small signs of use and age (smallest crack on the rivet on 1 corner). It comes in the original leather sleeve, also marked Weiss. It measures ca. 27 cm or ca. 11 inches long. Check the attached video on how to work your vintage man tool : slide rule operation instructions!