Back in the USofA both GM and Ford have what’s called restoration packages. You can call in with your vintage car’s informaion (VIN) and depending upon the brand and age, you can get a bunch of stuff for your car, including copies of the build sheets and configuration.
Does such an animal exist for Citroen? I actually registered at service.citroen.com and the website rejects my 1975 VIN. Google turned up a few things (static stats) so I now know my DS was the 1849th Break made in 1975.