The US Coast Guard issued a policy letter regarding the processing of merchant mariner credentials (MMCs) for mariners not requiring a Transportation Worker Identification Credential (TWIC). Recent legislation excludes certain mariners from the statutory requirement to obtain and hold a TWIC in order to receive a MMC. This policy letter advises USCG field units how to implement that requirement. CG-543 Policy Letter 11-15 (12/19/11).