The hammer is case hardened, which is what gives it the color. So is the trigger, which appears to be grooved. Hammers and triggers have been changed a lot over the years, depending on what was in fashion at the time.
What is meant by "transitional?" They have always been in transition.
It is true that S&W and others made better finished products back then because the labor rate was lower. One of the things they apparently did was finished off the grip frame with the grip in place, which is how the perfect fit was produced and why the grips you found at the gun show don't fit so perfectly. The grips may be marked with the serial number of the gun.
The gun also has that slightly matte finish that I like so well, though other finishes were produced as well. They all show scratches about equally well.