The Crossed Keys
Another of the symbols of the Vatican can flag and other papal insignia is that of the crossed keys to the kingdom of heaven. One key is silver and one gold key, the two bound together by a red cord. The silver represents the authority of the pope on earth and the gold his authority in heaven. The key is crossed in a saltire cross.
Nozedar Adele, The element encyclopaedia of secret signs and symbols, 2008, The Crossed Keys, p 155