What’s the exact process to identify a real 66 Formula S Barracuda?

Jim Lusk said
This car had EVERY standard Formula S item, but was not a Formula S. Also had a four speed and disc brakes. Yes, it was/is valuable. I changed the color, however (back in the 1980s).View attachment 1715784751 View attachment 1715784752

That's like my very 1st '66, which I still have. It has all the options, but, not a FS. It's also a heater delete car. Very unusual.