Rotary calculators - Marchant ABL

Harold Avery. One of the last rotary calculators made by Marchant, this is fairly typical of their standard machines. The proportional gear mechanism used in the Marchant line incorporated a nine-speed transmission in each digit of the keyboard. This, combined with the higher 1300 rpm cycle speed of the machine, made the Marchant the fastest rotary calculator available. Most Marchants (with the exception of the SKA and SK) did not have a control register. Instead, the machine was fast enough to calculate each digit of the multiplier as the keys were being pressed. This machine langushed in the storage room of an office building in San Francisco for 30 years.