If you see an article that was lost by a Jew, it is your duty to care for it, and return it to its owner, as it is said, "You shall surely return them."¹ 22:1. Similarly, any of your neighbor's property, that you are able to save from destruction, you are obliged to do so, for this is included in the mitzvah of returning a lost article.

footnotes: ¹ Deuteronomy

Although according to halachah, in a place where the majority of the people are non-Jewish, even if the Jew identifies it you are not obliged to return it to him, because we assume he already had despaired of its recovery, nevertheless, it is good and proper to do more than the halachah requires, and return it to the Jew who identifies it; and we force him to do this.² 259—Raviah If the finder is a poor man, and the owner of the article is wealthy, the finder is not obligated to do more than the halachah requires. In a place where you are required by civil law to return a lost article, you must return it in all circumstances.

footnotes: ² Shach

If you find an article regardless if it has an identification mark or not, if upon finding it, it was apparent that it had been placed there, such as a garment or an ax, that was left at the side of a fence;³ 260:10, Shach-Poskim. Otherwise, if it is in a totally unprotected place and bears a mark of identification, you must take it and return it to its owner. If it bears no mark, you may take it for yourself. If you found it in a place that is partially protected, if it bears a mark, you must take it and return it to its owner. If it bears no mark, you must not touch it; just leave it there (Ramah 260:10). If in the last instance you picked it up, the Ramah says you must hold it until Eliyohu, the prophet, comes and reveals who the owner is. (Shach 260:32) and even if it is doubtful whether they were purposely placed there, or lost there, it is forbidden to touch them.

footnotes: ³ Or any other place where it is protected. Ramah

If an old, respected man finds a lost article, that it is so shabby that even if it were his own, he would not carry it home, because it would be disgraceful to him, he is not obligated to bother with it. He should, nevertheless, do more than the halachah requires, and bother with it, even though it is beneath his dignity.

If you find an article and you do not know who lost it, whether it has a mark of identification, or does not have a mark of identification, these matters involve many divergent laws, and you should consult a Rav as to what you should do.