Question [Q] S3 SGH-I747 with Fake ROM GT-I9300?

Hi to everyone, I have in my hand apparently a S3 GT-I9300 because behind the battery says gt-i9300 and in settings/ About device/ Model number say GT-I9300 and PDA, CSC, CP Says I9300ZSALG3 But in Donwload Mode appear SGH-I747, the memory ram show 1.6 GB
I'm gonna show you some pictures of this confusion...
I have to say that i'm want to upgrade this phone to 4.3 but I don't wanna take any risk of brick for bad firmware.
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