Scale 1:48. Plan shows the starboard inboard profile, looking from port, an internal plan view below the flats and sections, as fitted of the U class submarines Undine (1937), Unity (1938) and Ursula (1938). A Vickers Armstong builder's stamp, dated 18 February 1939 is printed on the drawing. A Vickers Armstrong Principal Ship Overseer's stamp, dated 7 March 1939 is also printed on the plan. The signature of the Principal Ship Overseer is written in the stamp. Modifications in red ink to Ursula only, made at Chatham Dockyard, dated Febraury 1942 are included on the drawing. The plan shows the sections at Frames 10, 20, 31, 46 and 64 looking forward. A seperate section of Frame 10 showing modifications in red ink is also included. The drawing also shows the sections at Frames 72, 82, 92, 102 and 113 looking aft.