File:2018 Maastricht Heiligdomsvaart, reliekentoning St-Servaasbasiliek, voorbereiding 10.jpg

English: So-called "Key of Saint Servatius", as part of a display of relics and reliquaries in the cloisters of the Basilica of Saint Servatius in Maastricht, Netherlands. The objects from the church's treasury are shown here in preparation of the veneration of the relics in the church on Saturday 2 June. It is part of the Heiligdomsvaart ("relics pilgrimage") celebrations, a religious and historic event that takes place once in seven years and dates back to the Middle Ages. The Key of Saint Servatius dates from the early 9th century and may have been donated to the church by Einhard.