What I've tried so far is to make a Testing Sword, and then have the player enchant that and show it the guy you need to prove yourself to. Problem is, the reference to an item is deleted when you enchant it (and yes, this empties any alias it is in) and a new one is created with the enchantment. So, I have no idea what to run the dialogue conditions on.
I'd be willing to try anything, as long as it proves the player is a good enchanter. I just can't think of what it would be...