Can i ask what is a bank pass book and what is the objective of this mission? Seems very interesting but i have no clue what is going on here
In the olden days (at least some accounts) didn't mail you statements - you had a little book with blank pages, and every time you conducted a transaction, the bank would print that transaction as another line.
OP found such a book indicating he (or a family member)used to have an account that was forgotten about, so he's trying to figure out how to track it down, considering the bank is no longer in existence.