finder of lost property
Refers to the person who finds and holds lost property, often in legal or formal contexts such as the Japanese Lost Property Law.
The finder must return the item to the owner.
If the finder does not appear, the item is handed over to the police.
Compound of 拾い (ひろい, 'picking up, finding') + 主 (ぬし, 'owner, master'). The reading ぬし for 主 is a native Japanese reading.