Q: 1) I took a book out of the library and found an envelope containing money inside it.

2) I found a perfectly usable item in the garbage.

May I keep either of them?

A: 1) The envelope likely belongs to the last person who borrowed the book. Thus, if you can ascertain who it was, you should return the money to him if there are simanim. If you cannot ascertain who it was, you should publicize the item, as any other aveidah.

If the book is dusty and appears to have been sitting a long time, and the owner presumably abandoned hope by now, you may keep the money (C.M. 260:3, 262:5; Hashavas Aveidah K’halachah 12:9).

2) If it seems that the item was willfully put in the garbage, you may take it, even if there are simanim. However, if the item is a small one that may have inadvertently fallen in or been swept up, you should alert the owner.

If it is a communal garbage bin, you should publicize the item if it has simanim; if there is no siman, you may keep it (C.M. 260:11; Hashavas Aveidah K’halachah 11:7).