I do not believe in the world of authentication, Prada can be 100% authenticated. There is only a confidence level, a percentage that could hardly reach 95%. For those who claim that they can guarantee the authentication decision of a Prada bag without knowing its source, directly from a retail store or from an individual, they are either being ignorant or irresponsible.
As early as 2011, when Sitoy Leather Products, a Chinese leather goods manufacturer, was enlisted in the HK Stock Exchange, it started to disclose that it had been one of Prada's original equipment manufacturers for years. Prada not only manufactures in China for shoes and handbags, there were rumors, according to a friend of mine, who used to work as a consultant in the luxury industry, that Prada has deliberately kept a blind eye on a small amount of authentic products leaked into the Chinese secondary market, as a way to penetrate an early market. Many Prada products circulated in the resale market are within this gray zone and unlike brands such as Hermès, Chanel, or Louis Vuitton, Prada has a blurred borderline between an authentic or a replica product, because the same manufacturer that makes the real product might make the fake product too; the fake can be the real, and the real can be the fake.
Ironically, there are so many guides out there stating different rules to authenticate a Prada bag, but simply a few trips to a Prada store will debunk many of them.
One of the most commonly referenced theories of authenticating Prada is through its 'R'. Many authenticators state that the 'R' of the Prada logo should always have a notch taken out of its right leg. And any 'R' missing the notch will indicate a fake product. See image below.
I have paid numerous trips to Prada's stores in Bloomingdale's and Saks in NYC, and every time as I inspect the products there, I see this theory won't hold its stance. The 'R' should always has a notch on the print logo, but when it comes to the metal plaque, it's falling all over the place. In the following close-ups, you can see that each 'R' varies a bit from the other, while the source of the four bags are all from legitimate importers that supply to large scale retailers. A notch to the 'R' is important, but having it or not, does not suffice a decision that a Prada bag is real or not.