I have a Robe of Tears, the AC is supposed to be 9
http://everquest.allakhazam.com/db/item.html?item=19802 and when I
wear it, my AC goes up by 50 points.

I just bought a Shardtooth's Flayed Skin, the AC is supposed to be 14
http://everquest.allakhazam.com/db/item.html?item=3768 and
when I wear it, my AC goes up by only 17.

I sent a petition in game about it and the GM told me
to ask other Enchanters about it? That was no help. Has anyone else
had stats show up in their inventory window different than what the
item is supposed to show?