Dating faber castell slide rules

07 Sep

Each can rotate separately from the other, with a foot operated brake to lock the wheels while transfering calculations.

The diameter looks to be about 4 feet which gives a scale length of 150 inches, or 15 times the length of a standard slide rule.

The modern pencil was born in 16th-century England, where, in Cumbria, a major deposit of graphite was found.

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The long joint head of the compass is well made with two steels but the other hinged joints are much cruder being just brass.The graphite would be glued in place, hand-trimmed to remove excess graphite, and then a second piece of wood would be glued on top so that the graphite, which is soft, was fully enclosed.The wood would then be smoothed, polished, and varnished to bring out the grain.A Harling "Woolwich" case of electrum instruments (missing large compass, dividers & pencil bow).Under the large protractor there is a pair of vulcanite set squares and in the bottom compartment there are a set of marquois scales and a number of scale rules, all signed Harling.