Oke, I just found this out, while farming the Batterd Hilt, from the little skeletons in Pit of Saron.
I ran 2 characters, both being my own, and i already completed the both instances on them.
I knew it dind't let them enter the same instance, but i just grouped them anyway.
On the first screenshot, it is clearly visible that a green item dropped, and i disenchanted it with my enchanting character. As you can see in the text.
On this screenshot, the ID is clearly vissible.
Now, on this screenshot, the epic fist from trash dropped and wonder by wonder, i could let it be dis enchanted!
Here is the screenshot, showing a Complete different ID.
Hope this can make some people happy, it sure does for me
Cheers!