500 Đồng

By 1966, South Vietnam's currency was under severe inflationary pressure — the United States military buildup had flooded the local economy with dollars, driving prices sharply upward and pushing demand for higher denominations. The 500 Đồng was a direct response to that devaluation creep, issued as the piaster's purchasing power collapsed faster than the printing schedule could accommodate.

Thomas De La Rue handled production throughout the National Bank of Vietnam's higher-denomination series during this period. The watermark security on this note was modest relative to the counterfeiting threat the South Vietnamese government actually faced — North Vietnamese forgery operations were active and well-documented by the mid-1960s.