Engineer’s slide rule complete with separate magnifying glass mounted in a folding frame for attaching to the cursor (1965).
A conventional log/log slide rule used for multiplication division etc. The magnifying glass which is a rare accessory significantly improves the users ability to read the scales.
[The mark “765” is the date code used by Faber-Castell for July 1965.]
A comprehensive guide to A.W. Faber and A.W. Faber-Castell Slide Rule Models, Types and Scales can be found at https://www.rechenschieber.org/wordpress/wp-content/uploads/2022/03/Rechenschieber_Faber-Castell_ed8_1.pdf. Page 101 of this guide refers to this magifying cursor.