A badge affixed to the accessory of a yukkuri to signify it is owned by a human. Unlike dog tags, the badges come in several colors, the three traditional ones being bronze, silver, and gold, usually representing its worth, both to the owner and sometimes society at large. It is generally accepted that harming a properly badged yukkuri that isn't your own is a big no no, especially the upper two ranks. Sometimes a platinum badge is used for exceptional yukkuri, but these are few and far between.
Because of the value of badges, more distasteful yukkuri have caught on that being a pet equals easiness and sometimes will go out of their way to steal one.
Some authors might use badges to denote yukkuri with special roles, instead of being a pet yukkuri.
For example the flower badge in pool #1961