Aristo 815 Wärmepreisrechner pocket slide rule heat costs 1970 Germany

This larger size pocket slide rule is made by Aristo from Germany specially for calculating surrounding heating costs within Germany domestic market. It has the number 851 and also has a dedicated cursor, specially adapted for this model. On the back there are calculating instructions in  German. It comes in a generic unsigned leather sleeve. The case and slide rule are all complete and in very good condition with only small signs of use and age. The 2 blue highlights for 2 scales are still clearly visible. The slide rule measures an unusual 18 cm or 7 1/8 inches. Check the attached video on how to work your vintage man tool: slide rule operation instructions!