The name Type 20 originates from a French Ministry of War directive which ordered that all of its military units be equipped with chronographs which had a flyback function.

This function provided sailors and pilots with a quick and reliable device on which they could rely, notably for precisely calculating when to change course. They also needed to be able to precisely calculate longitudes in order to avoid making mistakes with regard to course and targets. Until that time, four separate actions had been required in order to achieve the equivalent of the flyback function (that is, to start the chronometre, reset it to zero and then restart it): start, stop, reset to zero, start.

With the Type 20 model, only two actions were required for the flyback function:

· The chronograph was started by pressing the button above 2 o'clock: the chronometre hand began to turn.

· The chronometre hand reset to zero and immediately began to turn again by pressing the button above 4 o'clock.

At the time when the Ministry imposed the Type 20, other specifications were required for military use:
The time-keeping dial had to be black and have two other counters at 3 o'clock and 9 o'clock. They indicated respectively the time passed in minutes and the time passed in seconds for a period of 30 minutes. The numbers and the hands were coated with tritium so that they could be read in the dark.