Due to the first world war, it was difficult to safely transport gold to Great Britain but the United Kingdom still needed new coinage produced. Therefore, The Royal Mint established branch mints in overseas territories. These were located at Ottawa in Canada, Bombay in India and Melbourne, Perth and Sydney in Australia.

Each of the Sovereigns produced by these branch mints carries their own mint mark just below the horse on Benedetto Pistrucci's iconic reverse design. 'C' for Canada, 'I' for India, 'M' for Melbourne, 'P' for Perth and 'S' for Sydney.