Yes, that was in the era when "standard" blue was more "bright" blue, as seen with the .357 Combat and N frame and .44 Magnums. It lasted until the early 1960s when standard turned more dull.
No mention in the letter because the "bright" blue was once again the standard finish like before the war, and no longer an extra cost option. And therefore it would not have the large capital B stamped under the barrel following the barrel serial # that the bright blue finished guns had when it was an optional finish.
Yes, high polish blued finish was standard in those days. Here's a Model 15-2 (1962) that we inherited from my wife's grandfather (Calif. Chief of Detectives)- it was his LE EDC in a suede Bucheimer clip-on holster. It has a beautiful finish.