Pyxide pédiculée/Pyx
Barcelone, seconde moitié du XIVe siécle.
Argent partiellement doré
Legs François-Achille Wasset, 1906
Cl. 14777

Which can be roughly translated as:

Pedestalled Box (box on a pedistal)
Barcelona, second half of the 14th Century.
Partially gilded silver
Bequest of François-Achille Wasset, 1906
Cluny catalog number 14777

A pyxide is a specific type of box used to hold the Eucharist until it is ready to be passed out to the parishoners.

More information on reliquaries can be found at Wikipedia and at the Metropolitan Museum of Art site.