Well, we have seen cars from a single DSO be optioned differently before. It calls into question if some cars from a single DSO (say #83-0113) could have included ones that were not optioned as SSP Mustangs.
I'm not saying that has happened, but it's hard to say with 100% certainty that every VIN in a batch with some confirmed SSPs are
all SSPs. I think cars ordered for specific agencies are all SSPs when they ordered them, but the DSO #83-xxxx cars
could (small chance) have some civilian models tossed in to mess us up.