This is a votive crown given to the Church by Reccesuinth, King of the Visigoths (649 – 672). It is gold filigree set with sapphires, pearls and other gems and is the best surviving piece of Visigothic metalwork. The letters hanging from the crown spell [R]"ECCESVINTUS REX OFFERET" (King Reccesuinth offers this.) The crown is at the National Archaeological Museum of Spain is Spain except for the "R" pendant from RECCESVINTUS, which is in the Musée de Cluny in Paris.
Images from Wikipedia.