Original: In 1974 he received his first posting to the United Nations, as First Secretary of the South Permanent Observer Mission (South Korea only became a full UN member state on 17 September 1991).
Simplified: At the time of Park Chung Hee's assassination, Ban was First Secretary at South Korea's Permanent Observer Mission to the UN in New York City (South Korea only became a full UN member state on September 17 1991).