In 1980 the dutch police used the old WWII M1 carbine to fire tear gas, using a pin in the muzzle on which a separate tear gas grenade was stuck, and a special blank cartridge to fire it. The multi shot tear gas guns in the movie were never part of the dutch police arsenal.
This movie takes place during the crowning of Beatrix, which was in 1980. Yet they use a VW Golf Mk 2, which wasn't released until 1983.
The Mercedes vans used for transporting the police units in the riot scenes are of the Kevlar plated type that was not available in April 1980. They were developed after the coronation riots.