Rare Cougar only GT emblems. The Mustang GT emblems had different stud locations. These were used on 1968 Mercury Cougar GT models.
This emblem shares the exact same pin locations with the 1968 6.5Litre emblem, so the factory could punch holes and installed the tubular nuts in the fenders of all S and X code Cougars, allowing either emblem to be installed. The 1967 GT emblems have an entirely different stud placement from these 1968 only badges.
Letter "G" is Ford part #: C8WY-16098-B
Letter "T" is Ford part #: C8WY-16098-C
According to the Ford Master Parts Catalog, these are the same emblems that were used on the 1971 and 1972 Cougars with the GT package.
Check out this article by the Cougar Club of America about the Cougar GT models: http://cougarclub.org/cougar-gt.htm