Mopar 413/426 Max Wedge block casting number confusion

Brooks James said
Is the "S" a different font ?

View attachment 1715996880

On this post the pad shows an "S". On my 1964 Chrysler 300-K (not RAM). At the far right of the pad after the "HP" there is the same fancy font "S". Has anyone every figured out what that indicates? Some sources say it indicates "special" but it does not say what is special about the engine.

Thanks, James