Fendi's serial numbers encode the model, never the date. What dates a Fendi is which MARKINGS it carries, and the markings changed in documented eras. Tell the guide what the bag has; it returns the era, and the one cross-check that matters.
The era brackets the bag; it authenticates nothing on its own, and every marking here has been counterfeited. The serial's first six characters name the model and the rest is production reference, so anyone dating a Fendi off its serial digits is decoding a code that carries no date. The real check is agreement: the era the markings claim must agree with the model's own documented birthday in these files. A Spy is a hologram-era bag by definition; a First exists only in the RFID years; a Baguette can be any era, which is why its variants carry the burden instead. Markings in the wrong combination, or a pouch with nothing inside it, are not curiosities. They are verdicts.