IWA 05173 Schnorr Tellerfeder Disc spring slide rule 1974 Germany

Interesting slide rule by IWA model 05173 in German made for the Schnorr Company in 1974. Can be used for calculation on metal round disc springs on one side and for normal calculating using standard scales on the other. It comes with the original small manual to describe the special side. It is in good condition with only small signs of use but there is a little darkening if the see through plastic (slide rule and cursor). It is fully functioning with all parts intact. It measures ca 18 cm or ca. 7 1/4 inches long. Check the attached video on how to work your vintage man tool : slide rule operation instructions!