your 6 matching serial # locations for fixed sight pre war Hand Ejectors and all post war Hand Ejectors thru ~1956.
NOTE: Observing serial #s for accuracy or even existence, especially on penciled stocks, requires magnification, bright light, and an attitude that it is there!
1. Gun butt - or forestrap on I frames/single shots with grips that cover the butt
2. Barrel - bottom of barrel or in extractor shroud
3. Yoke - on rear face only visible thru a chamber with a flashlight
4. Extractor star - backside
5. Cylinder - rear face
6. Right stock only - on back; stamped, scratched or penciled depending on vintage and stock material. (except most target grips because individual fitting not required.)
If there's a K prefix and the # is correctly read the revolver is from 1966.
Therefore by about the end of 1959, serial # locations went up to 4:
1. Butt.
2. Frame in yoke cut, and also stamped Mod 17-2 here on the frame.
3. Extractor star until ~ 1980 with the new extractor star shape.
4. Back of right stock, except most target grips because of less individual fitting, until ~ 1979 when no longer hand fitted.