As a result of this over-all design style and part number format, there are often very similar Faber-Castell rules which differ only in the body design, and essentially identical rules which differ only in scale length. Some rules also featured 'addiators' on the reverse side, to allow addition and subtraction as well as conventional slide rule operations. These combination rules are quite unique, and provided exceptional computing power in an all mechanical design. Want to know how these addiators worked? Click HERE and HERE to see the original directions from Faber-Castell.

A trademark feature of Faber-Castell Geroplast rules was the use of (generally pale green) color accent stripes on the primary scales (C+D) for quick identification. This technique was also used by Aristo (another German slide rule maker), but they used yellow as their trademark accent to match their packaging.

While their first rules (until 1946) were of 'swiss pearwood', there was a brief period (1946-48) where beech and (1948-1950) maple were used, after that period they were made of 'special wood' (a wood composite) with laminated scale surfaces. Later Faber-Castell rules were generally made of an engineering plastic called Geroplast (appears to be a type of PVC or Cycolac), with deeply embossed and filled scales. Geroplast and the pigment used to fill the scales sometimes 'bled', resulting in a colored bloom around scale markings, or faded accent stripes if left out in sunlight. Most later rules were 'self-documenting', and had their mathematical relationships symbolically noted on the right hand side of each scale. Some had an all plastic construction, with glued end braces like the 12/series, while higher end 2/ and 62/ rules had aluminum end braces, and were fully adjustable. Here's what the catalog has to say about the various types of construction.

Faber-Castell rules were some of the most visually striking rules ever made, and examples like the 2/83N (Novo-Duplex) are massive rules, with stunning design, and amazing color and scale accents. Compared to most North American rules, they are far more complex and have much nicer user features, including over-range scale extensions to reduce re-setting (reached below 1, usually to .8, and over 10, to 11 or 12), extra cursor marks for common tasks, self-documenting scales, color co-ordinated scales, anti-skid and anti-scratch bumpers to protect the rule and cursor, and exceptional craftsmanship. The Faber-Castell 2/83N in particular may be the finest slide rule ever made by any manufacturer.

Rules from Faber-Castell usually had green cases and boxes, and some had an unusual zippered case that was quite attractive, and especially useful for rules with addiators, as the closed case prevented the stylus from getting lost accidentally. Some FC rules (especially from the 2/ series) also came in a very nice clear and green plastic 'presentation' case, which showed off the rule even when closed.

Faber-Castell appears to have made rules for at least one other company, Dietzgen, to market under their own name, such as the Dietzgen 1741, 'Novo-Biplex' rule. The box for the 2/83N says that it is one of approximately 50 rules 'currently' offered by FC, so it is clear we still have a bit of work to do tracking down all of the modern models that were made.

Rule is self documenting on right hand side for all scales. A very powerful and beautifully made log log rule, equal to the K+E 4181-3, Deci-lon and Post versalog 1460, if not far better. Has pythagorean scale (P), expanded square scales, folded scales and scale over-ranges. This is the full size enhanced version of the 62/83(N) pocket rule. Rule shown is from my personal collection.

Rule is self documenting on right hand side for all scales. A very powerful and beautifully made log log pocket rule, equal to the K+E 4181-1 and Post versalog 1461, if not better. Has pythagorean scale (P), BI and CI, folded scales and dual cube scales (K, K').

Rule is self documenting on right hand side for all scales. A very powerful and beautifully made log log pocket rule, equal to the K+E 4181-1 and Post versalog 1461, if not better. Has pythagorean scale (P), CI, folded scales and dual square root (W1) and square root 10x (W2).