British D-class submarines larger as C-class according to the Dutch magazine Marineblad dated 1908-1909 no. 3

An item referred to the magazine Schiffbau reporting that the British test submarine D 1 was 0,5 larger as the boats of the C-class indicating a displacement of 450 ton.(1)

Note
1. The D-class submarines had in fact a displacement of 550 ton. The D1 was laid down at the shipyard of Vickers on 16 May 1908 and sunk on 23 October 1918 while being used as a target.