Scale 1:48. Plan shows the port inboard profile, looking from starboard, plan views of the superstructure top, bridge top and an internal plan view above the flats, 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.