Almost.......
So is the final answer. "S&W never sold a revolver with Pachmayr or Pachmayr unmarked grips?"
Well, that is almost correct. There is one model I'm aware of that came from the factory with Pachmayr Grippers. It was a model 625 (.45 ACP) produced in the late 1980s. There may be some other guns that were shipped with Pachmayr grips, but this 625 is the only one I recall seeing.
The rubber grips used by S&W from the 1990s forward were either Uncle Mikes or Hogue.