Explanation:

Illustration (a) to section 403
403. Dishonest misappropriation of property. 
Explanation 2- A person who finds property not in the possession of any other person, and takes such property for the purpose of protecting if for, or of restoring it to, the owner does not take or misappropriate it dishonestly, and is not guilty of an offence; but he is guilty of the offence above defined, if he appropriates it to his own use, when he knows or has the means of discovering the owner, or before he has used reasonable means to discover and give notice to the owner and has kept the property a reasonable time to enable the owner to claim it. What are reasonable means or what is a reasonable time in such a case, is a question of fact. It is not necessary that the finder should know who is the owner of the property, or that any particular person is the owner of it; it is sufficient if, at the time of appropriating it, he does not believe it to be his own property, or in good faith believe that the real owner cannot be found. Illustrations- (a) A finds a rupee on the high road, not knowing to whom the rupee belongs. A picks up the rupee. Here A has not committed the offence defined in this section.