1. This rule is the same as other 1/54 rules made at the same time except for one important difference - it has an addiator on the back. This compensates for one of the big weaknesses of a slide rule - it cannot perform addition or subtraction. Since the addiator can perform both these functions it obviously extended the usefullness of slide rules. What is interesting is that the slide rule and the addiator had parallel lives for a long time. The invention of the addiator is normally credited to J. L. Troncet of France in 1889 but similar designs had existed for a century or more. However the first patent for a slide rule/addiator combination was not obtained until 1937 by Carl Kübler of Germany (Slide Rules - a Journey Through Three Centuries - D von Jezierski, Astragal Press, 2000)
2 . This rule is a Darmstadt - named after the technical college in that German city.
3.  The log-log scales are on the rear of the slide and accessed via a plastic "window" on the back of the rule. This makes good sense, as whilst the log-log scales  are used in conjunction with the C and D scales for raising numbers to a   non-integer power, the result cannot be carried directly forward into other calculation. For example to calculate 2.5 * (6.1)^0.75 you would have to calculate the value of (6.1)^0.75 first, note down the answer and then multiply that by 2.5. Perhaps this explains why this layout was so successful over so many years.
4. The log scale and the trig scales are on the top and bottom edges of the ruler respectively and are accessed by extensions to the cursor. Although the cursor construction changed with different models, the same principle continued to be used.
5. The stock and the slide are of wood and have metal inserts.
6. For instruction on use of the addiator click here. For details of other Faber Castell 1/54s click here.