"he looked more closely at the ring with its skull - a masonic sign"
The Square and Compasses, a symbol of Freemasonry
GNU Free Documentation LicenseThe Square and Compasses, a symbol of Freemasonry - Credit: MesserWoland

 The Freemasons are a not-particularly-secret society who emerged in Europe around the beginning of the seventeenth century. The society involves a moral code that is evoked through the symbolism of stonemasonry, where God, or the Supreme Being, is seen as the 'Architect' of the universe. Meetings of Freemasons are highly ritualised events. The value of these rituals and allegories lies in their cabalistic nature. As the knowledge must be protected from outsiders in order to retain its value, complex and ever-changing secret passwords and handshakes ('signs', 'grips' and 'tokens') were developed among Freemasons to identify themselves to each other.