This model is an interesting development of the previous 16e model. Keys are square, and there are two separate keys for Additions or Subtractions. A small lever, to the right of the “Plus-key” allows to push the carriage from left to right, while another lever below the “Minus-key” allows the carriage to be pushed again on the left. Both shifts are not electrically-driven. The shift from right to left is made thru a wire of nylon attached to a wheel driven by a spiral spring.