Vintage Slide Ruler "Mentor-Fix 157/80"

Excellent condition, includes original case and original (Ephemera) paper instructions. Possibly made in 1972. Very rare. *12" / 10" Mentor-Fix format Mannheim Slide Rule Simple rule and manual, in an original Faber-Castell vinyl view case. Plastic body rule with side inch ruler, and multi-line cursor, with powerful folded scale arrangement. Rule face is self-documenting, with scale functions listed, as well as scale letters. Reverse has graphic illustrations for operation. (8 Scales + side ruler) Front - A, DF, [ CF, CIF, CI, C, ] D, K plus inch ruler Back - Graphic Instructions engineer, measurements, calculate, scientific instrument