In the 1998 National Defense Authorization Act, the Secretary of Defense approved awarding Cold War Recognition Certificates to all members of the armed forces and qualified federal government civilian personnel who faithfully and honorably served the United States any time during the Cold War era, Sept. 2, 1945, through Dec. 26, 1991. 
Applicants must certify that their service was "faithful and honorable", and they must supply a copy of a supporting document which proves that they served during the Cold War era. The certificate may be awarded posthumously to those whose relatives apply on their behalf. 
There is no charge for a Cold War Recognition Certificate. Note that no medal has been authorized or issued for Cold War Recognition. 
The program is scheduled to run for 10 years, so there is plenty of time to send in your request and supporting document.