IWA Iwamatic 1660 technical circular slide rule 1960’s Germany

This round slide rule, the IWAMATIC 1660 is of an interesting design and even received a German IFDESIGN award. It is marked IWAMATIC and was aimed at technical staff for more elaborate calculations than the 1650 for commercial use.  It’s patented construction features an inner ring that can be moved with one hand and rotated the inner two rings while the outer ring stays in place. The the disc with red cursor line can be moved separately as well as the red cursor line over the inner ring. On the back is a company logo printed. It is in great working condition with minimal signs of use and age and come in the original (non signed) black pouch. It comes with the original German manual as well. It measures ca 11 cm or 4 1/4 inches in diameter. Check the attached video on how to work your vintage man tool : aviation slide rule operation instructions!