There are a number of itemstyle constants in use which have not been given a proper name.
Lua Code:
ITEMSTYLE_UNUSED16 --Stalhrim Frostcaster
ITEMSTYLE_UNUSED19 --Silken Ring
ITEMSTYLE_UNUSED20 --Mazzatun
ITEMSTYLE_UNUSED21 --Grim Harlequin
ITEMSTYLE_UNUSED22 --Hollowjack