The early 1951 5 screw J frame Chiefs Specials had a half moon front site and a small trigger guard, As they evolved slowly changed to ramp Front site, elongated trigger guard , By 1958 it had become the 3 screw Model marked version we know today.
Left to right 38 S&W I frame 1950 Terrier 1951 .38 Chief special (1952 first J frame style) , 1954 .38 Chiefs Special


Pics would help.