Ima not sure but i think this is not real because every itemslot has own script for displaying those "DispalyID"
for example you can have DisplayID from ItemDisplayInfo.bdc where is inone Line filled Whole Set
but point is that "DisplayID" can be used for every Slot like Head,Chest,Hands Because item will load only needed part from DisplayID ...
head will Head.mdx hands will load texture and attachment
For Example ....
53978:1="LShoulder_Plate_A_01.mdx",2="RShoulder_Plate_A_01.mdx",3="Shoulder_Plate_A_01Black",
4="Shoulder_Plate_A_01Black",5="INV_Chest_Plate10",15="Plate_DungeonPaladin_B_01Purple_Sleeve_AU",
16="Plate_DungeonPaladin_B_01Purple_Sleeve_AL",17="Plate_C_01White_Glove_HA",
18="Plate_DungeonPaladin_B_01Purple_Chest_TU",19="Plate_DungeonPaladin_B_01Purple_Chest_TL",
20="Plate_DungeonPaladin_B_01Silver_Pant_LU",21="Plate_DungeonPaladin_B_01Silver_Pant_LL",
22="Plate_A_01Black_Boot_FO"
i see here shoulders,pants,gloves ?
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and soem of them are jsut Icon for item in Bag
56985:5="INV_Drink_11"