Today I traded two ??? Items to Drahban (Whitegate) and both times the result of the appraisal appears immediately after I execute the trade, and I recieved the item prior to the dialogue:

[Trade item to NPC]
Llana obtains a bone earring.
Drahbah: Hmmm...
This seems to be...
Drahbah: I have finished appraising your item. It is a bone earring!
I'll just put it in your treasure pool now.

---

[Trade item to NPC]
Llana obtains a gust claymore.
Drahbah: Hmmm...
This seems to be...
Drahbah: I have finished appraising your item. It is a gust claymore!
I'll just put it in your treasure pool now.