I suspect that the "S" is actually a "5" and the "1" is actually a "I" in the thread designation.
So, if I'm correct the designation should actually be:
Internal 7/16-14 NC5IF and 7/16-14 NC5IF
and
External: 7/16-14 NC5HF and 1/2-13 NC5HF
I ~ think this is an interference thread designation of the American National Course Fit, 60 degree Entire Ferrous class "5".