There are actually multiple offices. One inside the museum, and two in St Peters Square. One in the square is in a mobile trailer.
A few minutes after leaving the square I stopped and bought a postcard for a friend and the shop also sold stamps. Even though I was now back in Italy, I was given a Vatican City stamp, and I asked if it needed to go in a Vatican post box. The seller said no, just post it anywhere. I decided to walk back to St Peters Square rather than risk Italian post, because when Eva was there her postcards took a month to arrive at their destinations.
This stamp celebrates the 15th General Ordinary Assembly of the Synod of Bishops. It is a lovely colorful stamp.
The Vatican mail box outside the other post office in the square.
For more V-themed postage, head over to Sunday Stamps.