There is no written documentation I have ever come across that
there was ever anything called an Alto III.
The only follow on to the Alto II was the Alto II XM, which added
bank switched memory and a larger writable control store.
Alto II was a redesign of some of the Alto I for manufacturability
done in El Segundo.
Chuck Thacker did the "Dolphin", which was the first Xerox OIS
workstation. The 8010 is an adaptation of a paper design that
Butler Lampson did called "Wildflower"
The next machine Chuck worked on after the Dolphin was the
Dorado.