In 1986 the Royal Australian Navy celebrated its 75^th anniversary. The Australian navy had been founded in 1911 after a number of years of debate. On the one hand some said that as a newly federated nation, Australia should fund, man and administer their own naval forces. Others argued that the nation was better to rely on the Royal Navy and contribute funds towards this In the end the first group won out and the Royal Australian Navy was founded in 1911 with an initial fleet of three destroyers and a battle cruiser, the first of which arrived in 1913.  

By 1986 the RAN had matured into a well established military force and celebrations were arranged to celebrate this anniversary, including a fleet review in Sydney Harbour with six RAN ships being joined by ships from New Zealand, USA, UK, France and Canada. Among the souvenirs being sold were small pins such as this one: 

These were cheap little souvenirs that would have been sold in their thousands, but how many have made their way to the UK and still survive nearly forty years later is unclear, so this is probably quite an unusual little souvenir over here.