Originally Posted by smartasien
I have absolutely no idea if this is true or not but i saw it on a techpower up forum today "All depends of serial number. Ive read somewhere that on 550BE the 3rd letter indicate if you can unlock or not. H indicate you cant and Z you can."
Mine unlocks and the 3rd letter is a Z.
In any case you can exchange/sell if the 550/555 doesn't unlock.