First welcome to the site. Hope you find the information and support useful in your concours related endeavors. I invite you to explore and read allot of other threads. You will find allot of information and other details that may help you. Also, since you have a 68 Cougar, you will likely enjoy seeing the assembly line pictures the site purchased a number of years back. Look for them in the San Jose assembly plant section under the main The Assembly Line section. There are a number of them all have titles starting with 68 San Jose - xxxxxxxxx
If your thinking about the small square paper stickers San Jose didn't typically use this practice. San Jose only marked the car after inspections for paint in 68. Other inspections were verified/recorded on forms other than one we find on 68's on the hood latch support which sometimes appears to have been done by a paint inspector. Some paper and others applied to windows where the stickers were removed by the dealer before delivery
Related thread already posted
http://www.concoursmustang.com/forum/index.php?topic=7019.msg39708#msg39708