Manufactured from 1920 until the beginning of World War II, these models incorporate all of the improvements of the previous machines. The Comptometer logo is inscribed on their front and back panels and they have the red release key that was introduced with the previous two models.
The ST (SuperTotalizer) has two display output registers and two additional levers that allow for the creation of intermediate results. Each key pressed by the operator is added to the top display register creating an intermediate result which is added to the bottom display register when the operator activates the front right lever (it also resets it). The bottom display register accumulates the intermediate results until it is cleared by using the left lever.
These three models are the last of the shoebox design that was introduced in 1907 with the B model.
