Dec 1967 SJ built 68 J Code Cougar - rear license plate bracket is in good original (based on review here) galvanized condition. Coded 7 21 D2 which I thought was a '70s production code, but also looking here seems like that may be a Dearborn plant production stamp. Any thoughts on whether this is an original rear bracket for this car?
The stamped date codes on sheet metal do not include the year (check out the article in the library about date codes
Yours decodes to July 21st 2nd shift at Dearborn stamping plant - not Dearborn assembly plant
The only way to get in idea if the date is "in the range" for your car would be to compare other cars built around the same time as your Cougar that were built at San Jose also. Not sure if they were building enough Cougars to continually stamp these items or they were stamped in batches instead.
Looks like the face is still nicely galvanized but since the license plate will cover that its the inside that is likely more important for a finished car.
Date will be covered also. I would install and use it (if the condition matches what your going for) while you look at others to get an idea of the dates. Easy enough to change out later and keeps you moving forward in the mean time