This Ring has a shape that unlocks the sewer gate leading to the Rat's Den under Ghirardelli Square, San Francisco. It seems that such rings are worn by Ratmen.
A Ratman who was in Pier 5 apparently had such a Ring. Two Dragons went and assaulted him in order to take his finger. One left for the Shop in order to exchange the finger for chain snips.
Perhaps that Ring was then worn on the neck of a Dragon who attempted to enter the Den through Ghirardelli Square, with Noah Goring. He was attacked by a Ratman, climbed a gentry holding a neon sign but his foe killed him, and left his body there hanging.
Later the Manhunter climbed the sign and took his Ring with a Walking Stick. With it, he opened the gate to the Den.