TServo2049 said:

I wonder if this version is the sound mix that was on those clips sent to TV stations/etc. by Fox/Lucasfilm for promotional purposes. TV was still exclusively in mono, so would it be too much of a stretch that the clips sent out used a mono mix?

(I know I've seen a Siskel and Ebert episode from 1980, around the time ESB came out, which showed clips of the first film with the mono mix.)

Yeah, why I referred to Gregaton's comment was that I thought this may perhaps be another clue that this could be another theatrical mix and not just produced exclusively for 16mm prints, but I guess many TV-stations used 16mm back then. I was a little disappointed by the lack of info regarding the original release of ESB in Rinzler's otherwise superb making of book, there's some info about the shots they added at the end of the film in the 35mm version but nothing more. I had hoped it would've gone into more detail regarding the 70mm vs. 35mm differences and the theatrical mixes.