Seafarers' Identity Documents Convention, 1958 is an International Labour Organization convention concerning Merchant Mariner's Document.
It was established in 1958, with the preamble stating:
Having decided upon the adoption of certain proposals with regard to the reciprocal or international recognition of seafarers' national identity cards,...
An identity document issued under the convention or its successor is colloquially called a Seaman's Book or a Seaman's Card.
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Text from the Wikipedia article “Seafarers' Identity Documents Convention, 1958”, available under CC BY-SA 4.0.