I used to own a SAR-D, and if memory serves me correctly, doesn't the "D" stand for "defect"; as in the incorrect dial as mentioned above.
I think you are right; all the "SAR" nicknames are just that, nicknames; the actual Marathon name for the watches is "wrist watch, dive" I think:roll: as printed on the caseback for gov't orders. J was "Jumbo", C was "chronograph" T was tritium. G....hmmmm, I think that even though the plain luminova SAR was the first model, the Tritium G model was actually what was envisioned for large "Government" orders.....
If you do a forum search here on WUS, both in the dive forum and the pilot/military forum, you will find TONS of info. Also, don't forget that it originated on the MWR forum at broadarrow.net.
SAR myth and mythology....fun stuff, great watches! I've owned about 10, have none now, and MISS THEM ALL!!!!!!!!!