Open Sesame?

Holy Sophia! The book is actually a safe? COOL!
It truly must be the right book because the word wisdom (the meaning of Sophia's name) is at the bottom of the bookplate. WOOOHOOOOOO!

You need to get the book out of the basilica before someone stumbles upon you in the tunnels or notices the book is gone, but there's no sense leaving until you know the book safe opens. Let's see if we can quickly figure out the 3-digit lock code.


Take a look at the wording on the bookplate.
"Dedicated to she who was both wise and selfless. One who would open this book would do well to revisit the origin of the great lady’s legend. May the number of the reader’s days be thrice blessed."
The word number appears larger, and "thrice" refers to 3. And there just happen to be 3 digits needed to unlock the book safe!

As I recall, both the story about Sophia's origin and the Saliolum booklet mentioned an R.C. year with 3 digits. I can't remember it off hand, but could that be the number needed to unlock the book?