The Special Performance Vehicle door trim tags were used on Cougar XR7-G's through about the third week of March 1968. Most of these are Hertz XR7-G's, which were 200 of the first 202 XR7-G's built. All Hertz XR7-G's were built before any other XR7-G's with two exceptions that were built to be displayed at the 1968 Hemisfair in San Antonio, Texas. All XR7-G's were built at Dearborn, so there would not be any Special Performance Vehicle door tags on Cougars from any other plant.
I preach to anyone who will listen - if your car has the original door tag, do not replace it. Reproductions are available, and are easily spotted. A reproduction door tag in my opinion devalues the car significantly.