Gold disk VS regular disk?

I believe Mobile's claim was that gold is more malleable, reulting in better pits which can be read more accurately, therefore requiring less correction aka distortion.

With regard to earlier and later version of the same album, if they were manufactured in the US, early US plants had a terrible process quality problem. The yield of acceptables was very low and it took a long time for some plants to even come on line. Perhaps a lot of the earlier discs, although deemed acceptable, still had "bad pits" and required a lot of correction.