All PSA vehicles built after 01 Jan. 1980 have a 6-digit number stamped in ink somewhere on the body. From this, the so-called “ORGA” or “RP” number, one can calculate the day of production of that car. This is important when looking up technical service bulletins, since some only apply to vehicles manufactured before or after a particular date.
According to the available information, PSA started using this number 01 Jan 1980 with the number 1149. From that day on, this number was incremented by 1 every day, whether the factory was operational on that day or not.
Check the various labels in the door frames and look for a 6-8 digit code. The RPO sometimes has two digits appended to it, ignore these.