Found with Mordente reduction compass. Parallel rulers. Decorative steel or silver ends. One ruler with scale of equal parts (0-12, by 1) on one side, and a scale 3-21 with "D" at one end and "I" at the other end of the other side. Other rule with a straight line with "C" at both ends on one side, and a straight line with "I" at both ends on the other side.
