Library of Saints Director Sophia:
Did you say 1,6,6,7? Hmm... It's rare to see a book with only 4 digits... It must be a book written long ago. Because the number of books has dramatically increased, today 12-digit numbers are very common.
In fact, many of our earliest records -- including those with 4-digit numbers -- were lost in a fire several years ago.
Perhaps you will be lucky, however. Let me search...
"Thank you."