Russian submarines at Vladivostok identified as L-class by Japanese intelligence in 1938

A letter of the German naval attache in Japan dated Tokyo, Japan 2 March 1938 reported that the Japanese intelligence service identified the Russian submarines at Vladivostok as belonging to the L-class. Earlier was said H-class, but this was not correct. The H-classification was just used during the building.

Source

High Command of the Kriegsmarine (OKM). Case 36.  Website