I spent some time in the Boise State University Library today. Many books still have these old check-out logs in them. I went searching for books I checked out in the 1980s and realized something. It used to be that the student number was the Social Security Number...and so....thousands of people wrote their SSN in these books. Although that system of "check-out" is no longer used, the cards are still in the books. I saw plenty of SSNs in the section on Boccaccio. Some people also wrote their home addresses on the cards.