Stock Number: 9279


For sale antique comparison rule by Troughton & Simms. The rule is engraved with scales of English and Spanish inches, and old French inches. Contained in the original mahogany case.


13-1/2 inch (34 cm) long


c. second quarter 19th century

Country of manufacture

UK and Ireland

Category: Calculating


UNUSUAL COMPARISON RULE, English, c. second quarter 19th century, signed “Troughton & Simms, London.” This 13-1/2″ (34 cm) long brass rule is 5/16″ square in cross section, engraved on the four sides with scales of English inches from 0 to 12 by tenths, Spanish inches likewise, old French inches (the old “Pouces du Roy”) from 0 to 12 by twelfths, and “Decimetre’s” from 0 to 3 by hundreths (i.e., by millimeters). Condition is excellent, complete with its original slightly domed mahogany case.


The partnership of Edward Troughton and William Simms commenced in 1826, and was a long-lived manufactory of all manner of optical and mathematical instruments. We have had a number of interesting comparison rules, but none quite like this. It may have assisted in English trade with France and Spain, and was made at a time when the old French inch measure was not yet fully abandoned in favor of the metric system


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David and Yola Coffeen both have enjoyed academic careers, as planetary astronomer and as linguist/educator. But since 1982 (yes, 1982!) they have been full-time dealers in early scientific and medical instruments, under the name Tesseract. Selling primarily by catalogue (over 100 issued so far) they also have a web presence at www.etesseract.com, and can be contacted at [email protected].

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