"Also of interest to some may be that the 70mm prints of "The Empire Strikes Back" differed from the 35mm version in that some editing differences, additional shots, alternate takes, and extra dialogue can be detected through a comparison of the two versions. It is understood that when the movie was considered "finished," the elements were turned over to the lab and sound facilities so the desired 70mm print order could be prepared. The filmmakers, however, elected to "un-finish" the movie and make a few, albeit subtle, changes that, considering the expense and time involved in re-striking and and/or re-sounding 70mm prints, were reflected only in the film's 35mm prints. There is a bit of irony in all of this trivia: the majority of the public and media who saw the movie in its first month of release saw the "less complete" version."
At the time I hit a brick wall in my research, but I may soon be able to shed some more light on this issue.
I will soon investige this fully.