In case you don't remember, Lancia, after the fight with Xanxus, gave Tsuna his old Boss's Ring:

Now, the ring played a small part in the 10 years later storyline when a Strau Mosca detected the ring when Tsuna didn't bind it with a Mamon chain.

The ring hasn't been mentioned in the manga since.

The ring raises a few questions:
  1. Will the ring have a purpose in the next storyline?
  2. What's its attribute?
  3. What is the ring's rank?
  4. Who is going to use it?

My current thoughts:
  1. Maybe... It has been a long time since it was mentioned, but if the only purpose of the ring was for a 2 page problem and a flashy entrance for TYL Yamamoto, I'll be disappointed.
  2. Probably 'Sky', since it was a boss's ring and it was given to Tsuna. But I kind of like the idea that the 'Sky' attribute is exceedingly rare, so only the most powerful Mafia families would have sky rings as their attribute.
  3. Spanner said that the only 'A' rank soldiers that he'd heard of in the Millefiore were the 6 Funeral Wreaths before the 100 'A' rank soldiers he announced when the real 6 Funeral Wreaths were revealed. Also Lancia said that it was nothing special compared to the Vongola ring. So it's probably a 'B' rank ring... Maybe an 'A', since the 7³ rings are a lot more special than that.
  4. Either it's just a back up ring for Tsuna if the Vongola Ring gets taken from him, or he'll need to give it to somebody for their protection. I was half expecting him to give it to Kyoko or Haru when he told them about the current situation, but they shouldn't need it. Maybe if Iemetsu or the 9th is still alive and he needs a ring? I don't know.

So, thoughts?... Anyone?