Russia building 6 submarines for her Black Sea Fleet according to the Dutch magazine Marineblad dated 1911-1912 no. 7

An item reported that of the six submarines for the Russian Black Sea Fleet were 3 at the Baltic shipyard and 3 at the Nevski shipyard at St. Petersburg, Russia to be built. For the first 3 was a design of Burnow used, with a large range, for the other 3 an improved Holland-sign. Building submarines in series of 3 was a result of the experiences in Russia with combining 3 submarines in one group.