We can't find any source for this item (quests reward, drop, etc). It's highly probable this item is not obtainable right now. It seems that the New Sombra bélica is obtainable.
Have gotten 2 of these in a couple of hours farming the named mob. Seems to be watermarked, as I received GS 465 & 466 versions.
So you can't get this at 600 GS as it is dropped by a level 52 mob?