Tangent Sight; Attachment or Orientation Mounted to the Back of the Slot Elevation; The support is provided with a hook that engages in a square notch in the lock elevation; and is tightened with a screw from behind. A short square iron bar on top of a pyramid with grooves through the top; can move back and forth vertically. The set-up rod has two scales on opposite sides; one going from 0 to 5; the other from 0 to 4.5.; anonymous; Netherlands; 1845 - 1865; iron (metal); brass (alloy); h 14.5 cm x w 11.5 cm x d 2 cm