Editing Comptometer (section)

===Model A===
All the models, from this one on, have a metal casing, but the model A has a polished glass panel for the output display in the front. This model is produced from 1904 to 1906.

Described in patents 762,520 and 762,521, it introduces a new carry mechanism that reduces the power needed to operate the keys to one fourth of its predecessor's. It also introduces the duplex feature that allows for keys to be pressed simultaneously.<ref>Turck J.A.V., ''Origin of Modern Calculating Machines'', page 149-157, Arno Press, 1972, reprint of 1921</ref> And finally it introduces a simplified clearing mechanism that only requires one lever, and one back and forth motion of it, to reset the machine. "The machine gun of the office" as it was called in some World War I advertisements,<ref>''The Soldiers' French Phrase Book'', The Felt & Tarrant Mfg Co, advertisement page 54, 1918.</ref> was starting to develop the form and mechanism that it would keep for the next forty years.