Ok, so I did a guru search on the idfile of the weapon. Basically, this will return any item that shares the same graphics.
Search Results of Items with Similar Graphics
The only items that would have this graphic in Kunark were the Rod of Battle and the Nihilist Battlestaff. So, it's definitely one of those two items.
However, I would like to re-visit Nihilist Battle Staff. The item IDs that you originally posted were Allakhazam's IDs. Allakhazam assigns IDs based on when they get added to Allakhazam. A better indicator of when an item was added to the game would be the actual in-game ID which you can find on Lucy. For the Nihilist Battlestaff, that ID would be 12842.
http://lucy.allakhazam.com/item.html?id=12842
The IDs of 12840 to 12842 puts these items in the time-line of added at launch with Kunark. You can look at items with similar numbers
Here
Item IDs are not fullproof as occasionally an item ID will get modified instead of creating a new ID such as in the case of
these bad boys. Overall though, it's a pretty accurate way of assessing when an item was added to the game (different from it being acquired).
My opinion of this (for what it's worth) is that it seems to be the case that these Nihilists should be dropping their Nihilist gear at this stage.