Scale 1:48. A printed dyeline copy of a plan, showing the sections, as fitted for the Porpoise class submarines Porpoise (1956), Rorqual (1956) and Narwhal (1957). There is a Vickers Armstrong builder's stamp dated 17 March 1961 printed on the drawing. The plan shows the sections at frames 8, 41, 71, 76, 84, 94, 111, 114, 118 and 123 looking aft. The drawing also shows the sections at frames 23, 30, 53, 61, 65, 79, 98 and 105 looking forward.