There was a lengthy process of rebuilding, perhaps using some of the original material, in the interior court after the fire of 1483 which seriously damaged the east wing.
For Ruskin’s view of it in 1841 see here and there are photographs here.
At Notebook M p.84 and Notebook M p.85 Ruskin refers twice to the problem he has in giving a date for the upper arcade of the ‘three sides most aged of the palace court’, but he records his observations there on the same page as observations of the third order windows of the lateral facade. At Notebook M p.104 the windows of the ‘three old sides’ of the interior court are grouped with the 3rd Order Ducal Palace lateral windows of the Rio di Palazzo facade as a ‘great independent period’.
There is an extended discussion at Notebook M2 pp.137-139 of some of Ruskin’s puzzles about the dating and workmanship of the court.
[Version 0.05: May 2008]