The difference in the color of the bluing between the frame and the darker cylinder and barrel is not sufficient to suspect any parts change or a reblue. It's a 28, not a 27. Model 28s got an inexpensive satin finish and vary a lot from gun to gun. The top, bottom, front and back of their frame including the whole trigger guard were given a bead blasted appearance.
About 10 years ago an older member here asked how could a Model 28 be worth $500? My answer was pretend you are a youngster shopping for your first .357 double action target revolver on a $500 budget and report back on any better target revolvers that you find for the price. He had to concede there weren't any. That was 10 years ago!
While I bought my first Model 28, a new 4 incher, for $250 out the door, that was 37 years ago! I bought a new compact Toyota the same year for $5500, also out the door. What's a new Toyota cost today?