Yes, obviously if one has time on their hands and are allowed to actually "handle" the gun, you can look/see , some of the markings that tell you it is a "nickel" finish ,many folks don;t like it when you start to remove grips and take things apart to "find out" what-ever........I see so many that will not even let you pick and handle their guns......makes it tough at times.
Bottom line , in good light, one can "see" the difference in color 'hue'.....
run into this often with 'chrome' and nickel plating..............the parts, trigger, hammer, sights, may often help to "see" the stainless guns of various models, not all the time.