It says: "Mischief Managed" and it is from Fetching Tags. They can make custom tags with a phrase as unique as your dog. Ping and Norbert already have tags with phrases that are special to me so Weasley was clearly next in line.
Weasley's tag references the Harry Potter books that feature his name sake, Ron Weasley. The phrase "mischief managed" is used to conceal the Marauder's Map
a magical document that reveals the location of everyone inside the Hogwart's school grounds.
Of course Mischief Managed is also good phrase to describe a mischievous young pug as well. After all, Weasley manages plenty of Mischief!
We really like our Fetching Tags. Our communication with the company has always been great and the tags are sturdy and beautiful. Sure they cost a bit more then other tags, but a unique pet tag is a fun way to celebrate your dog's individuality.