Damaged Hertz horn marine mine Type II: German armed merchant raider 'Wolf'

Oval shaped German moored Hertz horn contact mine. The mine's four contact horns are missing, leaving four holes around the top. The base has a bracket which originally tethered the mine to an anchor. There is a 30 cm long hole in the base.

Damaged German marine mine recovered by the trawler Koraaga, off Gabo Island near the Victorian coast on 25 October 1929. The mine is believed to have been laid by the German armed merchant raider Wolf during the First World War.

Built in 1913, the Wolf began life as the cargo steamer Wachtfels, operating for the Hansa Line of Bremen. She was converted into an auxiliary cruiser in mid 1916. Outwardly, Wolf looked like an inconspicuous cargo steamer. However she was manned by 350 experienced sailors of the Imperial German Navy and concealed seven 5.9 inch guns, four 22 inch torpedo tubes, numerous machine guns, 450 sea mines (with laying equipment) and a small reconnaissance seaplane which could be dismantled and stored below decks.

In response to the British naval blockade of Germany, Wolf embarked from her home port at Kiel, Germany on the night of 30 November 1916 to disrupt Allied shipping. After entering the Indian Ocean to lay mine fields off the coast of Cape Town, Colombo and Bombay, the ship sailed eastwards to lay further mines in the Tasman Sea. Wolf entered Australian waters on 3 July 1917 laying mines off Gabo Island. The merchant steamer SS Cumberland was the only ship damaged by these mines, on 6 July 1917. The crew survived and the ship was beached. It later sank when being towed to Sydney in rough seas.

Wolf spent the next seven months harassing Allied shipping in the Indian and South Atlantic oceans before returning to a hero's welcome at Kiel on 24 February 1918. She had travelled 64,000 miles, sunk 135,000 tons of Allied shipping, captured 460 Allied prisoners, and not once pulled into port for resupply or repair - taking all she needed from the vessels she captured. All of her crew were awarded the Iron Cross, and her captain, Karl August Nerger, was awarded the highest decorations of each of the five German kingdoms, including the Prussian Pour le Merite.

Months after the sinking of the Cumberland, the trawlers Koraaga and Gunundal, manned by the Royal Australian Naval Brigade, swept the minefield off Gabo Island. They were assisted by the trawler Brolga and the tug Cecil Rhodes. They swept the area until February 1918 locating over a dozen mines, excluding this one, which was discovered 12 years later.

Hertz Horn mines had horns made of soft metal, such as lead, which contained a glass ampoule of acid. Contact with a ship broke the acid container, triggering a battery charge that activated the detonator. This mine is missing its horns and is badly damaged, probably due to a premature explosion.