From the announcement:
The PAVN weapons companies were equipped with an array of different armaments for a diverse number of roles. Much of the equipment was Chinese copies of either Soviet weapons or American equipment that was captured during the conflict in Korea.
For example, the Type 52 recoilless rifle was a copy of the American M20 75mm recoilless rifle and the Type 53 82mm mortar were copies of the old, but reliable Soviet 82-BM-37 battalion mortar.
Perhaps no piece of equipment was more important than the Type 54 12.7mm Anti-aircraft machine-gun. The American forces relied heavily on the helicopter for mobility, firepower and supply and any capability to threaten this dependence was welcomed by the communist forces.