Australia WWII Battle of Sydney 1945 Badge

Original era manufacture. Sterling silver reverse marked outline of the continent of Australia, displaying the inscription; For Meritorious Achievement, Above and Beyond the Call of Duty, Battle of Sydney 1945. Not really sure what this refers to, perhaps the Japanese attack on Sydney in 1942 and not awarded until 1945. 27 mm medal, suspended from a 40 mm pinback bar. Marked Str.Slv. on the reverse