The Merchant Mariner's Document (MMD), previously called a Z-Card, is a kind of Merchant Mariner Credential previously issued by the United States Coast Guard in accordance with the STCW guidelines, and, until completely phased out, remains one of the standard documents required for all crewmembers of U.S. ships with a Gross Tonnage of over 100. An entry-level MMD allows a mariner to work on the deck as an Ordinary Seaman (OS), in the engine department as a Wiper, or in the steward's department as a Food Handler (FH). With experience and testing, qualified ratings such as Able Seaman (AB) or Qualified Member of the Engine Department (QMED) can be obtained. The document is about the size of a passport, and contains the sailor's information regarding date of birth, the location of issue, nationality, and the shipboard duties he or she is qualified for.