Serial numbers are unique to each bag.
Sorry, but the bag on the pictures is a knock-off. You'll find that 99% of sellers who sell fake bags claim that they're genuine. Perhaps sometimes they really don't know what they have in their hands but most do, some even have nice little stories on how they got the bag and why they're selling it.
From these pictures I can tell you this:
The yellow tag is always a dead giveaway that the bag is fake.
The leather is smooth, not bubbly in the least.
The lining is shiny (looks sort of multicolored on pictures due to reflections) and from what I hear, soft while genuine bags have a yellowish, matte and more stiff lining.
The braiding doesn't go all the way up and down to the metal parts - another easy to spot sign of a fake.
The hologram is not a regular sticker and shouldn't peel of like that.
In the future, please post questions about authenticity in the Authenticate This thread, preferably before you buy...