Standard Slide Rules

Faber-Castell

Addiator 111/54A Darmstadt

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This unusual slide rule by Faber-Castell has a mechanical calculator built onto the back of it to enable addition and subtraction.
I don't know why, because I'd have thought anyone with enough know-how to operate a slide rule would be able to carry out simple
operations in their head. Anyway, it makes an interesting addition to a collection

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