have S&W 41 22 lr with a 4 - digit ser#387X when was it made?can someone help

gives me an idea when it was made looks like 1957,that is when they started producing them,according to an artical i read, left side 387x over model-41 i guess my next step would be to write S&W and get a letter,1958 started w/5 digits.thanks for your help.

is this muzzle brake w/ cocking indicator ? that is the older, more valuable model.