Beautiful gun, and very good price for a really nice piece.
Several things about the refinish.
If it is a true S&W refinish, the revolver would've been stamped with a star, typically under the grips, but also sometimes on the barrel flat, or where the yoke meets the frame. If you see this star, it means it went back to Smith for some work, that could mean it had trigger work, or something else done, but if it doesn't have that star, it wasn't done at S&W.
It's hard to tell from your pictures, but if any of the corners on the revolver are blended, instead of sharp, that would probably lead me to believe it wasn't a factory refinish, the same goes with any stampings that look washed out. I guess it's possible it was sent to someone like Turnbull to get done, but if I saw the star stamp, I would certainly say it was a Factory refinish.
Good find!
ETA: I have read with a factory refinish, Smith will change the cylinder to the proper finish, as it's harder to refinish the original cylinder, so it's more cost effective to just replace it.