Continuity mistake: During the big car chase the Audi S8 rams the Citroen, pushing back the headlights on the Audi but on the subsequent scenes in the town the front of the Audi is intact.
Continuity mistake: When Gregor tries to sell the case, he puts the Jeep into park (we hear the sounds of an automatic transmission, and in a brief shot of the pedals there's no clutch). But he jolts the car forward a minute later without shifting into drive.
Continuity mistake: At the end of the Paris car chase with the BMW M5 and the Peugeot, Jonathan Pryce fires a few shots at De Niro and Jean Reno in the pursuit car. One shot takes the left wing mirror clean off, and De Niro even jerks his head to the side in reaction to the shot. The mirror comes off in mid frame, and you can even see the adjustment wires dangling from the mirror base. In all subsequent scenes, the mirror is back on the car.
Continuity mistake: In the early scene of the arms deal, when they are waiting in the car for the arms dealers to turn up, Robert De Niro (in the back seat) is initially unshaven, but then later in the scene he is clean-shaven.
Continuity mistake: In the car chase after the bald guy with the suitcase, when his car approaches a fish market inside Nice, you can see a guy with a water hose running to the right, to avoid being hit by a car. His hose is connected to some point on the left, however in the following shot there is no pipe across the road.
Continuity mistake: After the first big chase scene, Robert De Niro is seen with the group in their hideout. As he treats the man who was injured, he puts the bottle of alcohol down twice.
Continuity mistake: In the apartment with Diedre, Seamus's hand jumps from the bottle of scotch to his side.
Continuity mistake: When Gregor is in the chase scene at the old stadium, he runs/falls down some stone steps and loses his wire-rimmed glasses. In the next scene, he is wearing them once again, looking over his shoulder for Sam, who is chasing him.
Continuity mistake: While chasing Deidre the dividers between the lanes change. Right after the chase leaves the tunnel all the views of the road scene looking back at the cars show a road with a solid concrete divider separating oncoming traffic. But all the "driver's eye" views of the road show a post and guard-rail type divider.
Continuity mistake: In a close up of one of the alloy wheels on the BMW during the big chase, the wheel has changed style to a cross spoke.
Continuity mistake: At the end of the chase in Paris, when the BMW falls off the bridge into the building site, Gregor leaves the car through the back door window. During the chase he sat in the front of the car. He had also fastened his seatbelts, which would have prevented him from falling into the back of the car while it was crashing.
Continuity mistake: In the ambush under the bridge, the police car which can be seen across the river is a Peugeot 405, yet by the time it reaches the people at the bridge and chases the Audi it is a much smaller Peugeot 205.
Continuity mistake: During the final chase, if you see Deidre's hair, you will realise that the window was sometimes open and sometimes closed.
Continuity mistake: At the end of the main car chase on the bridge Robert De Niro's car skids to a stop and has virtually done a 180 degree turn, but when the other car goes over the edge De Niro's car is sideways.
Continuity mistake: During the final chase the cars enter a tunnel and Jonathan Pryce starts shooting at De Niro's car. To avoid being hit De Niro drives on the outside and starts to overtake a car to use as a shield. The inside shot doesn't show this car, and when the driver gets shot in the arm De Niro's car is somewhat behind it.
Continuity mistake: When Frank and Deidre are in the car watching the villa and she climbs onto his lap to kiss him while he is in the driver's seat, it's clear that there is no steering wheel in the vehicle.
Continuity mistake: When the BMW exits the final tunnel before it crashes, there is a shot of the windscreen wipers moving up, but in the immediate next shot, they are down.
Answer: There's no way of knowing what was in the case. It is a plot device called a "MacGuffin," a term coined by director Alfred Hitchcock. It doesn't actually matter what the object is but is just something that drives the story. It can be any type of object or device such as a "secret formula," "enemy war plans," a "nuclear weapon," a "treasure map," and so on that the characters are either searching for or protecting. There was never any intention to reveal what it was. Its purpose is to motivate the characters' actions and tell the story. Most likely it was intended to be a McGuffin just to keep the audience guessing and thinking about the movie long after it ends.
raywest ★