They are essentially just nicer business strike coins with more of a chance of being proof like in reflectivity. All the mint did to make them was polish business strike dies and strike them at a slower rate of speed from business strikes. It's pretty hard to tell the difference between a nice business strike from fresh dies and an SMS coin imo. I think that's why the TPG tend to label exceptional coins from 65-67 with the SMS designation.
Do you think that there is any chance that, if cracked out of NGC SMS slab and resubmitted, it would get an MS grade?
I suppose it's possible although I personally wouldn't gamble on it. I'd imagine that the TPG's who have seen countless SMS coins might have some identifying die characteristics that are proprietary info known to only them.
