I think itemtype has to equal 8 to count for shield ac.
Whitestone Shield: type 8
https://lucy.allakhazam.com/itemraw.html?id=31316
GBS: type 10
https://lucy.allakhazam.com/itemraw.html?id=10404
Iksar Hide Manual: type 11
https://lucy.allakhazam.com/itemraw.html?id=5763
EoN: type 8
https://lucy.allakhazam.com/itemraw.html?id=2498
Orb of the Infinite Void: type 8
https://lucy.allakhazam.com/itemraw.html?id=25098
Of course these are live values. The history section does show a few changes made and when. I'd assume we are using values pre luclin.