[zeestephen]

Re: He could have been one of the last Marines to serve a six month tour of duty in Vietnam.

According to Google, the last Marine Corps unit in Vietnam was pulled out in June 1971.

[Widget Jr]

Last U.S. Marines to leave Saigon describe chaos of Vietnam War's end

There may not have been any Marine units in the South after 1971. There were still Marines in South Vietnam until the end. One of them, Lance Cpl. John Stewart, was 18 at the time.