I have a list of codes for a Cadillac if I recall, and I would guess 1SE is a package, denoting specific hardware described by the codes you have defined.
The list I have shows
1SA - package, option 01
1SB - package, option 02
1SC - package, option 03
1SD - package, option 04
I learned elsewhere that 1SG is package option 7 (California package)
Therefore I would guess 1SE is package option 05. I don't know what that package is. Comparison of a lot of window stickers and option codes might reveal something.
Just my guess.
(Editing - now that I have answered, I re-read the question and I see you already know most of what I wrote. Sorry - I was looking for an individual option)