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Lo sentimos, hay un problema.
Mejor respuesta: Well, it doesn't look much like his printed signature... http://www.highsnobiety.com/uploads/pics...
Then again, he could be one of those people who sign different every time... like myself ;) Besides, I can't help but to notice the "31/150" on the side (I'm pretty sure it serves as an authenticity code) . This, and the fact that although it's not an exact match, the general style of the signature is simialr, leads me to believe it may well be his own personal signature. I'd suggest you check with someone truly knowledgeable in John Mayer, like sending that pic to the fan club and ask them.