In Vatican

Holy See

The Holy See is the episcopal jurisdiction of the Catholic Church in Rome, in which its Bishop is commonly known as the Pope. It is the preeminent episcopal see of the Catholic Church, forming the central government of the Church. As such, diplomatically, and in other spheres the Holy See acts and...

 usage, an autograph letter is a letter signed by the Pope

Pope

The Pope is the Bishop of Rome, a position that makes him the leader of the worldwide Catholic Church . In the Catholic Church, the Pope is regarded as the successor of Saint Peter, the Apostle...

 in which he refers to himself as "I", or using the majestic plural, "we", as opposed to the more usual letter from the pope signed by a subordinate referring to the Pope as "he" and saying, for example, "The Holy Father has directed me to reply to your letter...".http://www.vatican.va/holy_father/john_paul_ii/letters/2002/documents/hf_jp-ii_let_20020119_mons-rangel_en.html