Denny,
I think the Mariner Blue code from 47-52 is the same code, Ditzler/PPG 10419 (as listed in the Tech-Tip).
The shade difference between 10419 and 10984 is unknown (and, in fact, as you point out, DuPont lists the same paint code for all years, 47-55). Both paints are a dark blue color (as seen in chip charts), a navy/mariner blue color. We'll see if this is confirmed by the paint (10419) that PJS obtains from PPG.
Tim
