Major twist in the 57mm story...Russia is about to induct it as a replacement for the ZSU-23-4....

I did not see this coming.  Check this out via TASS.

State tests of the promising anti-aircraft artillery complex "Derivation-Air Defense" will be held in 2019, they are planned to be completed in November. This was reported to journalists on Friday in the department of information and mass communications of the Russian Ministry of Defense.

"To equip the tactical subdivisions of the army air defense of the ground forces, the development of the 57-mm anti-aircraft artillery anti-aircraft complex is being completed," the report says.

The Russian Defense Ministry recalled that the complex was designed to fight cruise and aircraft missiles, unmanned aerial vehicles, tactical and army aircraft and helicopters, single rocket launchers of rocket launchers, as well as ground and surface lightly armored targets. The complex includes a combat vehicle with a cannon of high ballistics and ammunition rounds, a transport-loading vehicle and a maintenance vehicle.

“It is planned to complete state tests of the complex in November of this year,” the Defense Ministry added.

"Derivation-Air Defense" was first demonstrated at the forum "Army-2018" in August last year. The self-propelled anti-aircraft gun was created on the chassis of the infantry fighting vehicle BMP-3 and is equipped with a module with an automatic gun of 57 mm caliber.