Miramar Ship Index shows that she was a refrigerated cargo ship, launched 9th December 1911 by Ardrossan Dry Dock and Shipbuilding Co. Ltd., and completed in February 1912, for the North Coast Steam Navigation Co. Ltd. of Sydney.
Her length was 150 feet, and had a gross tonnage of 479, and flew the Australian flag.
She was sold in 1948 and renamed "West River" and was broken up at Sydney in 1950.

WAR SERVICE
There is an interesting article and photograph of the Gunbar detailing her service in the Australian Navy in the second world war at the link http://www.navy.gov.au/HMAS_Gunbar