A single metal circle holds all of your assembled solutions to the many locks and problems you've encountered in your life. The single metal circle was a gift from a girl who inspired you towards the girl you are today. She was so strong and so beautiful. You only ever got to know her through the ephemera she left behind. And yes, one of the keys is to the Basement of the hauptbahnhof. You had a few months where you were sleeping with a train driver, and you couldn't help but help yourself to his master key.