Adding machine, c 1910.
© Science Museum / Science & Society Picture Library
S & N adding machine by Seidel & Naumann, Dresden. The Seidel and Naumann adding machines used chain drives and a stylus. The numbers to be added were pulled down to the base bar and then appeared in the result window. Presing the lever A allowed the inputted figures to be checked before the machine reset, while presing M allowed faster work as each figure reset when the stylus was removed. Subtraction was performed using the complementary columns at the sides.