VERY FINE & EARLY BRASS SECTOR RULE - CIRCA 1790

This rule was found with a brass Gourdin à Paris dated 1788 level and brass diagonal scale rule (also for sale on this website). It measures 3 5/16" x  13/16" x 1/16" and appears to be metric gradations. Note on the back some numerical notations in ink that appear to be very early. Very unusual configuration ruler. Uncleaned as found.