Significance of the pin?

I think it originally belonged to Oscar Wilde. It also just seemed to have magical qualities. Like anyone that possessed it became famous.

It seems to be a symbol of sorts of individuality and artistic inspiration, and in the queer context of the film, also an emblem of "difference" and whatever that may entail. Oscar Wilde was gay, and every person who ends up inheriting the brooch is queer in some way, so it certainly represents a distinction of being outside of the norm.