We can't find any source for this item (quests reward, drop, etc). It's highly probable this item is not obtainable right now.
This ring dropped for me and was 598 GS, i then spend umbral shards to bump it up. Did not turn gold nor gave a third perk.
Yeah that's how these work, it only tunrs legendary if the third perk is 100% going to be a specific perk.