Vintage Sliding Ruler - Darmstadt

This rule is a Darmstadt - named after the technical college in that German city. Interestingly the city of Mannheim is not far away and whilst this is also the name of one of the other standard slide rule scale layouts there is no (direct) connection; Mannheim was a French artillery officer.

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.

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. The labelling of the scales also evolved. 

The stock and the slide are of wood and have metal inserts. The later model has added plastic at the back of the rule. The 1952 model I have, in excellent condition.

Located in Centurion PTA. Shipping cost is for buyers account.