Above is a reliquary showing a bone fragment (ex ossibus) of Saint Sergius of Radonezh, the humble, ascetic spiritual leader of Russia in the 14th century and founder of the Holy Trinity Monastery north of Moscow. Sergius is considered one of the most highly venerated saints in the Russian Orthodox Church; you can read more about him here. The bone fragment constitutes a first class relic and the reliquary was sealed by the Augustinians.