Spiritbinding ilvl55+ crafting equipment and breaking it down.

Or more specific, the Artifact/Class set available to you at lvl50, the Militia Off-Hand tool and Militia Wristlets all have a chance to convert into Rank 4 crafting Materia. Can't say how high the chance is, I haven't bothered logging the results of my ilvl55 spiritbond trips, but overall it feels pretty low, roughly 15% chance or so.