This is a monstrance, a liturgical object used to display the consecrated
Eucharistic host for adoration. The word "monstrance" derives from the Latin
"monstrare," meaning "to show" or "to reveal." Usually made of gold or silver,
it often has a sundial-like shape, symbolizing Christ's divine light.
At the center is a circular glass compartment, called a "luna,"
which holds the host upright. It is used in the Roman Catholic Church
and some Anglican and Old Catholic traditions during Eucharistic adoration
or processions.