Black infilled letting at top, with clapper. 8ins.(20cm)diam.
Submarine J4, built at Pembroke dock and commissioned in 1916 as a new type of long-range, high speed submarine, the only class to be fitted with triple screws and capable of a surface speed of 19.5 knots, only slightly less than a contemporary Battleship. Transferred to the Australian Navy in 1919, she operated out of Geelong, Victoria. She was paid off in 1922 and subsequently sank at her moorings in 1924. Refloated, she was scuttled in the Bass Strait, off Port Phillip Heads, Victoria, in 1927 where she is now a popular historic diving site.