There is a thread here (short):
The evidence of the various dealers who sell “restored” cars is pretty patchy. On the face of it, most seem to indulge in cosmetic restoration only, paint over rust etc. So they might buff the paint, fit a new hood, new seat covers, paint the wheels.
These places aren’t looking for cars with rotten sills; too many imponderables impossible to budget for.
Of the 3 NBs he has, two had rust undersides (so expect lots of underseal), 1 had a suspect passenger sill, but not evidence of repair, so suspect a cosmetic repair in the past.