As we have learned, someone who finds a lost object is obligated to announce it and return it. Since he must return it in good condition, he must care for it while he has it. The previous Mishna (28b) described how a person must care for an animal; the Mishna on our daf discusses what kind of care must be given to inanimate objects like scrolls, clothing, metal utensils, etc.
According to our Mishna, seforim (usually translated as “books” but in this case they are scrolls, like a Torah scroll) should be opened and read once every thirty days. If the individual does not know how to read, he should open them and roll them, but only in a manner that would be ordinary use, i.e. he should not study something that he had never learned before, since it would wear out a specific page, nor should he study with a partner, who might pull the scroll towards him, leading it to tear.
In the Gemara, Shmuel teaches that someone who finds tefillin in the marketplace can establish their value, place the money aside for the owner, and use them. Ravina objects that the simple reading of the Mishna does not seem to indicate that the finder can establish the value of an object and then make use of it. Abaye responds to Ravina by saying that tefillin were commonplace in bei bar Ḥavu, while seforim were not.
Bei bar Ḥavu – the house of “bar Ḥavu” – was a large family enterprise in the city of Mehoza where tefillin and mezuzot were manufactured. The people from this family who worked there are mentioned in a number of places in the Talmud as experts in their field. Since this factory existed, it was not at all difficult to find tefillin for purchase, and if someone who lost his tefillin received their value in return, it would not be difficult for him to buy a new pair. Seforim, however, were much more difficult to buy, so it was important that the original scroll be returned.