Suggestion for the model 12:
I have a 1903 manufacture 1897 Winchester pump that I got from my Dad when he died in 1988. I do not know who (or when) refinished that old shotgun but it is beautiful, functional and very easy to care for. It has so very strange "black chrome" finish. It is shiny in the shade (the lower the light level, the brighter it shines), however if it is in the bright sun, it looks black. Easist gun to take care of I own. wipe it down and you are done. Not one speck of rust, fingerprints or anything. Sorry I can't tell you who did the finish, or even if they are still alive. Dad's 1897 has always looked like that as far as I remember (and I'm old enough to draw SS, and have for the last few years.)
For the S&W, I would reblue it if only to stop the rust. S&W would do the best job, but probably would be the most expensive too. There are others out there that do good work, it's not rocket science.