Monstrance from De Toren clandestine church

From the Rijksmuseum record

Roman Catholics believe that the consecrated bread is literally the body of Christ. The Host thus became an object of veneration, and containers were made in which to keep or display it to the faithful. The monstrance (from the Latin word for ‘to show’) is the most important of all of the Host containers, as is underscored by its sculptural design and the precious materials used to make it.