Mark, I have the same and I think Ben has it too (if he doesn't, I did send a scan of the very same page to him). That's why we think some models were produced with the Multimatic and Rollermatic transmissions simultaneously. Ben has a document that I don't have that he told me says more about the transmission change. I hope he could scan it for us!
Also, if I understand correctly, not all models were available in all colors... The model I have (WDR-64) was made only in white. The Custom Imperial was made only in white and copper (that means the colorized green set on Bewitched would have been coppertone!). It also means the white-colored WIA-64 had the Rollermatic transmission while the other ones still had the Multimatic at the time of the change of agitator.
The documents I have are covering both US and Canadian models and there's no information about Canadian models ever having the Rollermatic transmission. I know that Canadian models were also a bit different in configuration. For example, there was no equivalent of my US-built WDR-64 or DDF-64 here. Instead, there was a WCDRC-64 and a DCDFC-64.