It's weird, there were accounts that during the SE restoration, some parts had to be separated by film stock, presumably they had to un-cement the splices, and so forth. There was that anecdote about a space battle scene with a shot of Han where the chemical bath completely dissolved the emulsion.

Maybe only the effects scenes (and shots before/after wipes) were in the o-neg fully edited? I know separate o-neg exists for every individual shot that had effects added (which is why the first shot of R2 and 3PO shakes much less violently, why the remaining original-shoot components of the infamous landspeeder shot are nowhere near as grainy, how they were able to recreate the wipes, and so on).

BTW, the black line in the Vader shot looks like a tape splice (as opposed to a cement splice). Interesting that it's black and not white. Presumably that means the splice was done at a positive generation, not on the negative? This also could lend credence to my theory, related to AntcuFaalb's about the negative not being fully spliced together, that the JSC and GOUT elements were each edited, from scratch, at the interpositive stage.

Judging by the lack of the Tantive orange items and Greedo subtitles, I still think the JSC source could have been one of the earliest fully assembled positives of the film, predating the element used to make the '77 release prints.

EDIT: I just remembered that the JSC source also had printed-in *negative* splice marks (white lines, mentioned in another thread). Meaning it wasn't COMPLETELY spliced together at the positive level...