Pre 1840 architects scale rule

I have had this rule for 35 years and never seen another one despite numerous searches, the scales are on both sides.

It is a scale rule for use by architects, surveyors, etc. It is unusual in that it is 23 inches long. The majority are 12 inches or even 6 inches.

It was undoubtedly made by Stephen Norris Cooper, rather than Sarah as it dates from before the 1840s.

Before that date, scale rules, or scales as they are commonly known, were face marked. That is, the different scales were marked on the face of the rule and the dimensions were transferred to the drawing using a pair of dividers. By the 1840s, the professional user was working with bevelled scales, marked on the edge, like modern scale rules.

The line of measure (the name for the markings on a rule) on a scale of the 18th and early 19th century were mostly "lines of equal parts" – which is what your scale is – or diagonal scales with the divisions at the ends of the scale marked with a diagonal (nonius) scale. On a line of equal parts, each inch is divided into 30, 35, 40 etc. parts which gives the distinctive pattern that you can see on your rule.

Stephen Cooper began his business in London in 1809, working at 119 Great Saffron Hill, but in 1811, relocated to Shudhill, Manchester. He worked at 25 and then 16 Miller Street (these were almost certainly the same premises as there was a considerable amount of rationalisation of street numbering in the late 18th and early 19th centuries – before that it was often very haphazard! Sarah Cooper, who was undoubtedly his widow, continued the business at 16 Miller Street from 1847 before Josiah, again almost certainly their son, took over in 1858. It was very common for a widow to continue to run the family business after her husband’s death, particularly if there were children to take over in due course.

it measures 2 ½ inches x 23 inches long x ¼ inch thick mahogany