A reliquary's material tells you how valuable the parish or shrine considered its contents, gold, silver, enamel and rock crystal for major relics, plain wood or metal boxes for minor ones, with body part shaped reliquaries, an arm or a head in silver, built specifically to house a matching bone.
Construction and authentication
Made by goldsmiths and jewelers rather than church craftsmen generally, an important reliquary often has a rock crystal or glass window so the relic can be viewed without the case being opened. The relic inside is not just placed there, it is normally accompanied by a small authenticating document, called an authenticum, and the case is sealed with wax bearing a bishop's seal, a physical guarantee that it has not been opened or tampered with since a competent authority verified it.
Who may break that seal
Opening a sealed reliquary without proper ecclesiastical authorization is treated as a serious breach of custody, not a matter of curiosity, and relics are handled only by clergy acting with that authority. When a relic's authenticity is later found doubtful, which has happened to a considerable number of medieval relics over the centuries, church guidance calls for quiet withdrawal from veneration and respectful disposal, typically burial, rather than public announcement or discarding it as a fake. The container itself, once separated from a withdrawn relic, is sometimes repurposed for a different, verified relic rather than destroyed.