I doubt very much that Wick73 will believe me or accept anything that is said here, but others might be interested in my conclusions and why I reached them. With the understanding that I am going by pictures, here is what I see.
The top of the barrel has a number of areas that look very much like they were rusted, and then plated over. There was some attempt made to remove that rust without removing the markings, but that was only partly successful.
The side pictures show the top strap and the hinge rounded off; those areas are always flat, with sharp edges. The sideplate seam is visible and obvious, indicating that the sideplate was polished while detached from the gun. S&W polished the sideplate and frame together, and the seam is nearly invisible on a "like new" gun. The screw heads are buggered up, clearly indicating that the gun has been worked on a lot; that would not necessarily mean it has been refinished, but it does mean that the gun was disassembled many times, whether for refinishing or for repairs. Either way, not a good sign for anyone buying or appraising the gun.
The overall finish does appear to be nickel (not chrome as many refinished guns are) but has been scratched and worn after the plating was done. The hammer and trigger are plated, something S&W did not do and even a careful re-plater who knew guns would not do, but which many small plating shops did as a matter of course.
So when was the refinishing done? I don't know, but given the wear on the finish I would say it was done some time ago, and the gun used a fair amount afterward.
Jim