In the opening scene, a 1998 Volkswagen Passat is seen. That car was not available when the movie was set.
Donkers is brought to court in a police van. This is happen to be a Mercedes-Benz Sprinter which was not available in 1991. The license-plate is fake also.
As Adri and the assignee are looking at a drawing of the new sport school, they are actually looking at a drawing of a detail from a window.
The sponsor of this film is mentioned on a window, but the company did not exist in the period the movie is set.
In the scene where the first hit on Klaas was executed, the shots taken on the street before the garage, you can see a white van in the background with a modern day yellow license-plate. The yellow license-plates were not introduced in Holland until years later.
When they start a business. They want suits. They went into Suitsupply. But Suitsupply started in 2000.
In the opening scene when Klaas gets shot, there's a black Porsche 996 in the background of the shot. This model became available in 1997.