Kent, I disagree, the 1968 and 1969 versions were the most refined highest quality of the 960 series and they still used the Zenith belt drive changer (1969 was the last year) and the addition of the contour tone control made it more flexible.
Also, the 68 and 69 versions changed to silicon transistors in the tuner and preamp, quieter and more reliable.
I own a 1966 version as well as the 1968 and while they sound about the same, the later version has a more quality feel in the controls and the contour control is more useful than the previous presence control.
I also own a 1971 version, it uses the same amp and speakers but has that gimicky touch control preamp and a dreadful Garrard changer(they went to VM changers in 1972-75. It also uses some particle board in certain areas of the cabinet. But
it still sounds ok but different. They changed the crossover frequencies and changed some circuitry in the preamp to make it much more bass heavy even without the extended bass engaged. It lacks the
transparent openess, accuracy and coherence of the previous models. In short, it sounds more like a console instead of high fidelity.