That is very, very nice and a very desirable revolver! A 4" 57 is on my list to get someday.
Also, it's quite interesting that the stocks aren't diamonds. 1968 is generally accepted as the switch-over year. That must have been one of the earliest guns with the "new" style grips. They have excellent character and look perfectly fit from what I can tell of the mating at the backstrap. Also interesting it's RR/WO - not as common then and I think (but I am not sure) a special order feature, not regular production. I may be mistaken on that, but it occurs to me as I look at that nice gun. Congratulations again.