At no time have I received any ingots of 'Tier 3 Advanced Lacunus'. This material only appears as one metal in a rare drop blade seemingly made of disparite metals, which is not possible for a player to craft.
Elite Knights are dropping untiered 'Advanced Lacunus', which seems to me to be an error.
I have one of these blades as well. I usually forget it is there, then when I see it again I wonder how there are two dissimilar metals.