Final update from National Maritime Center on Fiscal year 2019 partial government shutdown

Merchant mariner credentials and medical certificates (national endorsements only) that expired in December 2018, January 2019, February 2019, March 2019, April 2019, May 2019, June 2019, or July 2019 will remain valid only until August 31, 2019. No further credential extensions are authorized.
Source: USCG
Link: Final update from National Maritime Center on Fiscal year 2019 partial government shutdown