Faber Castell 398, 10" (with magnifier *2)

This is a very nice and quite rare Faber Castell slide rule with magnifying glass cursor. The rule is marked A.W. Faber "Castell" , "DRGM" and "Castell 1/98/398". Mahogony base with celluloid, early 1900's. The lens can fold flat when not in use.

D Scale length: 500 mm. Significant digits: 3.3 to 4.