Something interesting comes up if you search for Pope pers (The Capital P makes me think Pope)
https:// chris-intel-corner.blogspot.gr/2013/12/the-popes-codes.html
This is about Code Breaking the Vatican correspondences during WWII. Someone posted a link at the end that takes you to:
http:// discovery.nationalarchives.gov.uk/results/r/2?_q=hw%2012%20vatican&_ps=60&_srt=3
Any codefags on that can see if this has any fruit?