The arms of the Canton of Genève are basically the same as the arms of the city, see there for the history. The only difference between the arms of the city and district is the sun above the district arms. This sun is used since 1540 to distinguish the two arms. The letters IES are the first three letters for Iesus, and are used as a symbol for John Calvin who started the Reformation in Genève. The sun symbolises that the city has found the light of the Lord. The sun with the letters was also used often on coins and other objects of the city.