Books, theft and preventive inscriptions

In centuries bygone, when books were a precious commodity, the fear of someone walking off with your books was an ever-present reality. Hebrew books can often be found with signatures and inscriptions by previous owners who in an effort to deter theft would at times write some entertaining inscriptions. On the other hand, there was also a reservation about writing in holy books, as it was perceived as disrespect to the book (see sefer Hasidim siman 281 and 698). What resulted was a delicate balance of inscribing your name, but subtly apologizing for doing so.

In a book I was just cataloging, I found the following inscription on the free-end:
אף על פי שאסרו חכמים
לכתוב על הספר, אבל משום סימן מותר
 מפני שיש אנשי מזימה
כשרואים ספר בלא כתובה וחתימה
נוטלים אותם תחת הגלימה
ואומרים שלי הוא מימים ימימה

loosely translating as:
"Even Though it has been forbidden by the sages
To write in a book, but to create an identifying mark it is permissible
As there are scheming people
when they see a book without an inscription or signature
place it under their garment
and say it was mine from years gone by"

The famed Michel Yitzchak Rabinowitz (1879-1948), bookseller and owner of the publishing house Darom once recounted: On a visit to the city of Lida, he visited the town's Rabbi, R. Yitzchak Yaakov Reines. The Rabbi welcomed him in and brought him in to his library and told him that he never allows anyone in to his library unless he is standing with him for fear of books disappearing but Rabinowitz was allowed free reign in the library.

When asked to explain his preferential treatment, Reines explained that an average Jew is suspected of stealing books, but for a bookseller, books are a matter of business and money, and I wouldn't suspect a Jew of stealing money (Minsk, Ir Va'em, page 610)