Antique 18th Century Lignum Vitae Brass Folding Rule Ruler French or German

Description

This gorgeous 18th century rule was likely made in Germany or France. Stamped "Braunschweig" near the brass and steel tip.. Features a dark wood body, possibly lignum vitae, with hand stamped numerals and brass tacked graduations. A swiveling brass tongue extends the rule to 24". Excellent condition.
Each inch on this rule is 15/16", indicating its age. The reverse is marked up to 50 in 5's, but does not correspond to modern metric measurements. Each "5" is equivalent to 2 modern inches. Not sure if this is an obsolete national unit or a special use measurement. The last 3 photos compare these graduations with modern units. A unique tool indeed.
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