Um,
I have "never" seen chrome on the plastic center section on any 68! My 68 "S" is just Argent on the edges and black along the sides of the plastic fins. 69 is when I seen solid black centers!
I have only seen two or three cars with the chrome and they were all untouched original Formula-S cars. I have also seen untouched original Formula-S cars without the chrome. I have seen a few of the inserts on eBay with the chrome since I started on eBay in 1999. With Ma Mopar you never know what shows up.