The Keys of Heaven also known as the Papal Keys was representing the metamorphical seat of Saint Peter. It was usually seen in the Papal Coat.
Behind the Meaning Edit
according to Roman Catholic teaching, Jesus promised to Saint Peter, empowering him to take binding actions. In the Gospel of Matthew 16:19, Jesus says to Peter, "I will give you the keys of the kingdom of heaven, and whatever you bind on Earth shall be bound in heaven, and whatever you loose on Earth shall be loosed in heaven."