Patens

Patens are small plates used to hold the of. They are usually made of precious metal.

In 1794, during the French Revolution, the monk Dom Poirier listed a set of three patens in the town of Saint-Denis. While searching for the Isu Temple beneath Saint-Denis, the Assassin Arno Dorian and his ally Léon recovered the patens and discovered that, with light and when put together, the plates revealed the location of the Temple.

Reference

 * Assassin's Creed: Unity - Dead Kings