Anybody know what it does?

Nothing. Sell it for the money.

You can use the table at the end of the guidebook to see which item does what. I used that table since there isn't really any good in-game way to do it.

ok, thanks, I hadn't thought of that

What a strange item.

It is not a quest item.
It is marked as equippable, because equipping it does not produce the error for non-equippable items.
However, it is not equippable by any of the classes that exist.

Attempting to use it tells me it has no use.

If I believe the hintbook. It's a neutral item. Which might matter, I suppose, if it could be equipped.

So it's a useless equippable, non-equippable neutral item.

I think someone goofed when editing the item table.