Breguet MARINE ÉQUATION MARCHANTE 5887 Mode D'emploi page 21

Reading the date Date
The day of the week is indicated in the aperture D at 10 o'clock, the
English
retrograde hand C points to the date and the aperture A / B at 1 o'clock
displays the month, year, and leap year (1/2/3/L).
Example: Saturday 14 January of the 1st year following a leap year.