What rarity are Theme Recipe Fragments?

On Quests, Theme Recipe Fragments might be found. However, their rarity isn't a usual one. So, what rarity are they? Theme Recipe Fragments

They seem to be given special importance, as a rarer object does; they always get on the "Quest Rewards" Screen.


Themes are a different 'category' of object and do not have Common/Rare/Legendary classifications (hence the grey backdrop).