Thanks for the replyes!!!!
Reading so, i'm convicted that those headphones are fake!
Really, the original senn PX 100 ALWAYS comes with the hard-plastic carrying case with the headphones folded in to the case, and both of them are visible when the box are closed. I also noticed that the pads are so thinner than the pads of the legit PX 100, and the plastic used on the blister package have a cheaper feeling than a original sennheiser package.
Searching on the net, i found this thread from fakeheadphones.com that says about those fake Senns PX 100:
fakeheadphones.com » Blog Archive » Are You Happy To Recieve A Pair Of Counterfeit Sennheiser PX200
After that, i've no more doubts!
Thanks, one more time!