Sheikh `Abd al-Rahmân al-`Ajlân, lecturer at the Grand Mosque in Mecca
You have to announce what you have found in public places for the duration of one year. You should during that period seek out any information that may lead to the owner. If someone claims it and is able to describe it in accurate detail, then you have to give it back to him. Otherwise, it is yours.
If someone thinks he cannot handle this responsibility, then it is better for him not to pick it up in the first place.
Source: Islam Today