This model has two columns of nine white plastic keys. Digits and complementary digits are indicated on the keys. Keys for odd digits are concave, those for even digits are flat. The mechanism is of steel and the two numeral wheels have white plastic rims. There are no subtraction levers, but there is a zeroing crank on the right. The entire model rests on a wooden base; there is no cover. The model was used as reference by Dorr E. Felt and J.A.V. Turck in developing the mechanism for production of the Model A Comptometer.