Coin found off Arnhem Land coast could be among Australia's oldest foreign artefacts:
http://www.abc.net.au/news/2018-07-10/suspected-kilwa-coin-discovered-off-arnhem-land-coast/9959250
http://www.abc.net.au/news/2018-07-10/suspected-kilwa-coin-discovered-off-arnhem-land-coast/9959250