Not Quite the Same

An explanation of MSTS ship markings and designations from the January 1963 All Hands, a monthly magazine for US Navy personnel.

MSTS (Military Sea Transportation Service) is now called MSC (Military Sealift Command), whose ships were/are  manned by civilian merchant mariners rather than regular navy officers and enlisted.

No indeed, MSTS was not the same as the rest of the navy!