Silver Papal Pius XII medallion - 1957

This is a lovely medallion for Pope Pius XII with his profile on the front and the vatican/St Marks on the reverse. Inscribed in latin around the edges but I think the date 1957 is there. No idea what it's made from, it feels like silver but there are no marks I can see to help so will sell as a silver metal piece. It's still in it's original small shiny paper wrapper.