The original grips on the old model single action Rugers (3-screws) were black eagles on a silver medallion. The grip screw and esctucheon were also blue.
Sometime around the April-June 1971 period, Ruger swiched their medallions to a silver eagle on a black background, keeping the blued screw and escutcheons.
In 1973, after the advent of the New Models, Ruger went to a stainless screw and escutcheons.
Hope this helps. Take care, and RKBA!
BB45C