A guy I used to work/hobby with could tell you which factory a Mustang was built in, and though in my era (1990s) the markings had all been gone, it is said that he and others could even tell you the name of the guy who assembled certain parts by the markings or other inconsistencies. When restoring a Mustang, these details (e.g. built by Mario in Dearborn in early 1967) are replicated by a good restorer. I believe that Jaguar also has affectionados who know the cars to that level of detail.