See Īrmy and USMC service in Vietnam is usually well documented in the Military Personnel Record. There are limitations and the requirements change periodically. The Department of Veterans Affairs is the agency that administers claims for illness related to Agent Orange exposure, usually as a result of service in or around Vietnam. Uniformed Service Qualifying for Veterans Preference Purposes.Wars, Campaigns and Expeditions of the Armed Forces Since WWII which Qualify for Veterans Preference.