Shchit-2 was a Soviet-era missile created to protect the Almaz military space stations from foreign threats.
An example of the missile is currently displayed in a restricted area at NPO Mashinostroyenia, a rocket design bureau based in Reutov, Russia, alongside an earlier version - called the Shchit-1.
The Shchit-1 featured a 23mm cannon and is the only gun to ever be fired in space, reported The Drive, as far as public information suggests.
The Almaz programme was a hidden effort by the Soviets to weaponise their space station - which was just a civilian endeavour as far as the rest of the world was aware.