There were actually (14) of these cars. I used to own one of them. They were all virtually identical and were made to go out to special events to show the new 1970 models. They went to Convention Centers and Auto show events. There were several unique features on these cars.
1) The trim around the back Fastback glass was Stainless Steel
2) The tail light bezels were chrome, just like regular production 1970 Mustangs.
3) The Boss stripes behind the rear wheels going towards the rear bumper, went thru the quarter panel light. They were put on before the quarter panel lights.
4) They all were the same color with virtually identical options
5) They all had the Mach 1 anodized aluminum trim pcs on the rear tail light panel. They did not have the plastic honeycomb pc but just the (3) trim pcs.
These were very unique cars that may be hard to explain at car shows, but there are several photos of these cars out there from back in the day.