Good eyes. They wear these on their tails. As with all things Shugo, the size and value of the thing denotes class.
Now I could just sell this, but you never know when you'll need a favor from a Shugo. Makes much more sense to me to find the owner, and give it back to them.
Do you have time to return this, [Player Name]? There are a couple of Shugos I see around here a lot--it could belong to either Sarinerk or Padinerk.