Simple peep site with two apertures and ivory notepad on back of arm. Ivory pencil holder threaded into crossbar with nameplate. Three pivoting sun filters - green, red and gray. Brass index arm held in place with thumb screw. Initials: "SBR" located on ivory arm between 45 and 50 degrees. Octant sits on three brass legs. Sitting arm of frame has index stop. Missing end plate on half glass. Two step instrument case originally designed with pivoting catch and lock - lock is missing. Bottom of case branded: "BAKER & HOOPER". Two paper tray labels in top - earliest reads:"GEDNEY KING & SON, #7 BROAD STREET, BOSTON NAUTICAL INSTRUMENT MAKERS" "ROBERT MERRIL MATHEMATICAL MAKER, 149 MAIDEN LANE CORNER, NEW YORK" (1838-1865) In black marker: "73" on step up. Blue marker: "73" on lower step Cork space on inside of box.