Audacious Theory

Exploration Stage: City Hall
From: Detective
Description: All these inventions by the Collector are really suspicious. It's unbelievable that a single person could know so much. I've read about a secret organization of Knowledge Keepers that existed in the City and I'm almost sure that our Collector was one of them. Alas, without evidence, it's just a theory. But these Keepers had special headwear that doubled as passes into their secret meetings. If the Collector has one of them, we'll definitely find it here! Will you help me find it?
Completed: You found a Master's cap! Look at this strange symbol that's drawn on it. It seems, my theory is right!