Such reliquaries were made to contain the relics of Buddha, usually in the form of pieces of stone or crystal. This piece compares in shape and lotus features with the set of five (registered as National Treasures) in the Saidaiji Temple Collection, Nara.1 The sharpness of the sculpting of the leaves is characteristic of Kamakura period bronze altar piece sculpture, and the manner in which the gilt is worn away shows how the reliquary must have been carried around for some ritual reason over many years.
1. Busshari to Hoju: Ultimate Sanctuaries: The Aesthetics of Buddhist Relics Worship, (Nara National Museum, 2001), No. 53-2.