That's immensely interesting - because all of the letterboxed/squeezed widescreen bootlegs have the "opening-day" composites. (Only the cropped mono-mix bootleg has the later ones.)

That would mean that there were at least three interpositives/print masters/whatever assembled in 1977. Based on my theories, they'd be:

1. A "pre-release" one with no orange marks, original composites, and splices (between each negative "roll?") have copious amounts of cement residue

2. An "opening-day" one with the orange marks (how were they introduced? were they dark orange damage on the positive, or light blue damage on the negative?), different splices, still the original composites

3. A "revised" one with the orange marks, same splices as #2, and new composites

All the 35mm prints used in fan projects (IB Technicolor prints from the UK, 1983 Spanish-language LPP print) seem to be from source #3.

I'm still not sure which source was used for the 70mm film cells (which came from a new, non-sound-striped positive made in 1995 - actually, all three films were taken from unstriped prints, I now realize the black stripes on the Empire and some of the Jedi cells were actually printed-in edges from a previous negative generation). Anyway, as you said, the one frame I found with a splice matches #2/#3. Here's another frame (look, blue lightsaber!) http://www.ebay.com/itm/171527475689

Would still be curious to see the Cineavision Super 8.