Griffin's heart, Doga's Artifact, Unne's Mirror and Rat's Tail.

You need to have bought all four of these items at the auction house and sold them in Treno for the Magical fingertip to appear. I remember having to start again to get the Excalibur because one/some of the items only appears/ed exclusively on previous disk/s and was no longer available, I can't remember what that item was though.