The U.S. Coast Guard vessel documentation
program is in transition from the old Marine Safety Information System (MSIS) to the new Vessel Documentation System
(VDS). Until VDS is fully deployed at or about January 1, 2002, the Coast Guard will only be issuing Certificates of Documentation to U.S. commercial vessels engaged in the foreign trade.
Other commercial vessels will be issued letters showing their name, official number, and the trade in which they are engaged. Regular Certificates of Documentation will be issued to these latter vessels after VDS becomes fully
Source: HK Law