Wiktionary
classification society
n. A non-governmental organization that establishes and maintains technical standards for the construction and operation of ships and offshore structures.
Wikipedia
Classification society
A classification society is a non-governmental organization that establishes and maintains technical standards for the construction and operation of ships and offshore structures. The society will also validate that construction is according to these standards and carry out regular surveys in service to ensure compliance with the standards.
To avoid liability, they explicitly take no responsibility for the safety, fitness for purpose, or seaworthiness of the ship.