Selected officer candidates in the Vietnamese Navy attended the Naval Officer Training Center in Rhode Island. This cover was sent in 1973.
A typical training program went like this: Quang Trung Training Center for basic training. If you tested high for English aptitude, you were sent to the Boat School in Saigon where you were taught English by U.S. Navy and civilian contractors. Some Finns even taught English here. Students were housed in two large ships anchored in the Saigon River in front of the Vietnamese Naval Headquarters. Those who did well at Boat School went on to train as officers. During the "Vietnamization" period, the high number of candidates resulted in some being trained in Australia.
VNNOC = "Vietnam Navy Officer Candidate"
IOCS = "International Officer Candidate School"
Thanks to Vinh Nguyen for this information.