I think some of the older post in this topic have some very incorrect information to them. I can’t say if there was an initial version downmixed to just stereo for the earliest showings for stereo optical prints. I don’t know if we have any of those prints left. From what I’ve found so far, the initial release had different end credits. This is preserved with the Moth3r widescreen bootleg and Puggo Grand. Both of of these have the same voice for Beru as the 70 mm and the Dolby Stereo mixes. Quite different from the mono mix (along with all the other changes). It is an interesting question whether there was an early stereo mix. But the 6 channel and Dolby Stereo Matrix mixes have identical mix stems. There are no differences and this is the source for all the later mixes (1985, 1993, 1997, 2004, 2011 - which differ as to how many of the changes made to the Mono mix were incorporated back in). As Star Wars was not the first film to feature Dolby Stereo and as the 70 mm (for which there is an in theater recording from 1977) prints were some of the earliest shown, I very much doubt that there was a different 2 channel plain stereo mix. It would have been just as easy to run the 4 main channels (minus the one or two LFE channels) through the encoder to make the optical track. As there were no changes from the early 70 mm prints to the main run Dolby Stereo prints, the tale of a separate 2 channel plain stereo makes no sense.