EXQUISITE “HALF THE KING’S FOOT” RULE, French, mid-18th century, signed “Duhamel à Paris.” This folding brass rule opens to 6-7/16″ (16 cm), and is divided on one side with a “Demy Pied De Roy” scale of six early French inches (“pouces”), the terminal inches divided into twelfths of an inch (“Lignes”). Both sides bear the most elegant symmetrical patterns of hand engraving. A lovely rule, in very fine condition, by Jean-Jacques Duhamel father or son.