written in the anouncement sticky thread
Unique items (August 29th, 2002 until September 29th, 2002)
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Several items in the game are "Unique". This means that you should not be able to have more than one of such item at any time. This means one item only, be it in your bank, inventory, a container, or wielded / worn. Unique items have the word "UNIQUE" at the top of their description.
Currently it is possible to own several Unique items of the same type. However, this is not intended - i.e. it's a bug - and it will be fixed. We have not decided on what will happen with multiple Unique items of the same type on characters when the fix is done, but will give proper notice of this before the change goes into a patch.
We will not ban people for owning several of the same Unique item. However, I would suggest you do not wear / wield several of the same Unique item