Which of the following is NOT a type of Coast Guard license?

The Merchant Mariner Credential (MMC) is an official document issued by the U.S. Coast Guard that serves as proof of a mariner's qualifications to serve on vessels. It is not a type of Coast Guard license by itself, although it may include endorsements that allow the holder to operate certain types of vessels or perform specific duties.

In contrast, the Master and OUPV (Operator of Uninspected Passenger Vessels) licenses are specific types of licenses that authorize the holder to operate vessels based on their size, type, and the number of passengers they can carry. Marine Engineer refers to a classification related to vessel operation as well, but it is considered a license type due to its specific nature in marine engineering.

Thus, identifying the Merchant Mariner Credential among other recognized licenses highlights its role as a comprehensive credential rather than a standalone license category.