Cylindrical Slide Rule Calculator by Loga, Switzerland, 1915-1920.

The Loga Company made this pioneering drum slide rule in Switzerland during 1915 - 1920 under the registered patent of the designer Heinrich Daemen-Schmid from Zurich. It consist of a paper-faced aluminum cylinder, 59 cm long X 15.5 cm diameter, and a sliding outer grid cylinder 32 cm long (with margins). The whole is mounted on an oak frame and protected with an arched oak cover. The total length including cover and handle is 69 cm (27 inch). In this slide rule, 1 log unit (from 100 to 1000) is divided along 60 consecutive and parallel scales. There are 60 scales printed around the circumference of the inner cylinder. On Each scale the numbers drawn are logarithmically divided (scale #1 starts with 100 and scale #60 ends with 1000). Since the actual length of each scale is 50 cm, the total length of all scales sums up to 30 meters. This total is therefore divided into 1 log unit only, which makes this slide rule very sensitive and accurate. The outer grid cylinder is only 27 cm long (without margins) with 60 parallel scales as above. In a small area on the right border of the paper, the printed numbers are smudgy; otherwise the condition is good. Special size shipping rate apply.