The Pr.123K represents an upgraded iteration of the Pr.123-bis MTB. In 1950, the Soviet Navy required reinforcement of the Pr.123-bis hull due to the transition from American Packard petrol engines to domestic M-50 diesel engines. The original hull structure couldn't withstand the demands imposed by these new engines. Moreover, with the discontinuation of the production of the DShK 1938 heavy machine gun, the designers opted to replace it with twin 14.5 mm KPV heavy machine guns. Additionally, these upgrades included advancements in electronics, encompassing navigation, target acquisition, and a friend-or-foe identification system.

This vessel was introduced during Update 1.79 "Project X" when the Soviet fleet was introduced into the game. The model was equipped solely with twin 14.5 mm KPV heavy machine guns, contrasting the earlier model's configuration of two twin 12.7 mm DShK heavy machine guns. Despite having half the number of machine guns compared to the previous model, the KPV proved formidable as a heavy machine gun, capable of inflicting significant damage on enemy boats and certain armored vessels due to its API ammunition. Furthermore, it carried two 45-36NU torpedoes, ideal for targeting slower-moving vessels or lower-ranked destroyers and frigates. Additionally, it carried four BB-1 depth charges, which, if used correctly, could destroy enemy boats and cause massive damage to enemy destroyers.