The U.S. Citizenship and Immigration Services currently issues very expensive Certificates of Citizenship and Certificates of United States Naturalization. They are printed by the Treasury Department's Engraving & Printing and then issued after vetting and a fee of approx. $600 dollars plus is paid to the U.S. Citizenship and Immigration Services.
Converting these certificates into plastic card identifiers would cost less, extend their life cycle, and be much easier to carry and submit when necessary. The former certificate could be replaced with a formal (framable) letter from the President.
The newer plastic cards could then be positioned for future design capabilities - for example biometrics, enhanced machine readable security printing, and encrypted chip technologies as needed.