LV generates a unique identifier for every single item, and puts them on a blockchain. Like Bitcoin. They cannot be copied or modified without ruining the entire chain, which is held privately by LVMH. So noone from the outside can add new items to the database. Each identifier contains the exact date (not just the week) and a long list of other data about materials, manufacturing, etc... that is all tied to the RFID chip that is sewn into the products.
Vuitton can scan the chips in stores with their iPads, and check the data on their blockchain for authenticity and other info. If they are generous, they will open it up for clients, so they can also access some data with their phones. But surely not everything.
You can hunt for the few last items they have with an old stamped code, but soon only some unpopular items will be like that on the shelves. But what the code did, these chips do it 1000x better. But at the moment, you need to ask LV to decode it for you. But the original codes were also not meant for us anyway.