Soviet submarines 266 type (model 50) under construction in August 1936 according to report No. 9711 dated 19 February 1937

An item referred to the report dealing with the training exercises of the Soviet Baltic Fleet in August 1936. It supplemented the reports 9697-7040 and 9699-7040. Three 266 type (model 59) were under construction at the Balti Shipyard, one was already almost completed. Another three of similar type were at the same shipyard under construction. While the construction was still in a early stage was it difficult to determine the type of the last three boats.

Source

National Archive. Record Group 165: Records of the War Department General and Special Staffs Series: Security Classified Correspondence and Reports. File Unit. Russia: Navy - MID 2503-16 THRU 2503-265. Roll 1443.