Goofs

When Barry disguises himself as Lt. Fakenham and crosses to Prussian lines, he rides wearing riding boots; in subsequent scenes, with the woman farmer and Potzdorf, he wears infantry gaiters.

When Capt. Potsdorf first encounters the so-called Lt. Fakenham, in most instances the former refers to the latter using the British pronunciation ("lef-ten'int"); but on at least one occasion he uses the American pronunciation ("loo-ten'int").

When Lord Bullington interrupts the music recital to announce his leaving home, his hairstyle goes from fluffy and covering his forehead to being combed hideously upward while verbally blasting his stepfather, then returning back to it's previous fluffy state after his mother goes crying off, just before an enraged Barry springs from his chair and starts beating him.

When Captain Potzdorf is heading into the fort under attack by the Swedes he walks, sword drawn, through a shallow trench whose sides are strewn with dead and wounded Prussian soldiers. In the left foreground, a corpse lying on his back with his eyes open, shuts them as Potzdorf approaches.

When Lord Bullingdon is alone trying to write out some work with Bryan Lyndon after the tutor has left, the amount of space remaining on his page varies between shots.

When Barry and Lord Bullingdon fight a duel, a coin is tossed to determine who shoots first. When alternate shots are taken in a pistol duel, the challenged always shoots first and the challenger shoots second. Barry should have shot first followed by Lord Bullingdon.

French soldiers are seen firing repeatedly from single shot rifles without reloading.

When the narrator announces the death of Sir Charles Reginald Lyndon, he situates his place of death in Spa, in 'the Kingdom of Belgium'. However, Belgium wasn't an independent Kingdom until the revolution of 1830.

When Lord Bullingdon is returning back to challenge Barry for duel, he is walking slowly in the corridors of the mansion full with drunk people. On the table on the right is visible a Dom Perignon champagne bottle. Actually in the 17th century Dom Perignon was a monk who experimented with sparkling wines, but the bottle and the label appeared at the end of the 19th century.

When Barry's son asks Lord Bullingdon for the definition of 'quadrangle', he is wrongly given the definition of 'quadrilateral'.

The narrator states, early on, "About this time, the United Kingdom was in a state of great excitement". The United Kingdom came into being in 1801, when it merged with the Kingdom of Ireland, before which it was known merely as the Kingdom of Great Britain. In fact the Act of Union of 1707, which joined England and Scotland, refers to "the United Kingdom of Great Britain" or "the United Kingdom" throughout the text. "United Kingdom" was in common use at the time of the film.

In one part of the film, Barry is rowing a boat peacefully on a lake with a dog sitting obediently in the boat. The dog is a Yellow Labrador which was first bred in 1899. But though it's not yet christened as "Yellow Labrador" and not yet intentionally bred, there's no reason why a dog like this shouldn't exist in that time.

Beginning at 23:08, as Barry is being offered cash to end the dual with Captain Quin, a car's headlights can be seen in the woods across the lake traveling from left-to-right. The headlights disappear behind a tree at 23:20.

However, if you look closely you'll see that it's a bird, with flapping wings, flying in front of the tree-line over the opposite shore. It's clearly visible across the entire screen when not blocked by the characters and a tree trunk on the near shore. Kubrick was noted for his attention to detail and multiple takes - if it was a car it is very unlikely Kubrick would've used that take.

In the short scene where Barry is cutting firewood with an axe, the wood in the pile and the piece he is cutting all have cleanly sawed ends. If he had a saw, he would be using it, as an axe is a useless tool for cutting wood--chopping and splitting, yes, but not cutting.

When Barry and Bullingdon fight, there is a map of the world in the background, with a decorative picture of a steam train on it. The film is set in the 1700s, but the steam train was not invented until the 1820s.

The glasses of the older robber are 20th-century. There were no nose-padded glasses in the early 18th century.

Captain Potzdorf and Colonel Bulow (the commander of the Prussian regiment into which Barry was pressed), wear mustaches. No officers in the Prussian army wore facial hair, with the exception of hussar (light cavalry) officers. Facial hair fell out of fashion for gentlemen (and therefore, officers, who were considered gentlemen), from the end of the 17th century until after the beginning of the 19th. Mustaches became common in the German army only after that time.

In an early scene of Graham looking over the Lyndon family expenses; bundles of receipts are held together with staples. Staples weren't invented until 1866.

When Barry meets King George III, it is mentioned that he "has raised a company of troops" and sent them to fight in the American Revolutionary War; the king encourages him to raise another and to go with them. However, the very next scene shows Lady Lyndon signing a bill dated 1788, five years after the war in America had ended.

The position of Lady Lyndon's fingers while playing the harpsichord with the orchestra. The fingering is close, but certainly not correct.

Brief camera shadow on Lyndon's back, just before the fight with him and Mr. Toole.

When Barry first meets Capt. Feeny and Seamus they are sitting at the inn. Barry doesn't even dismount and rides on, yet in the next scene there's a big tree over the path in the forest and Capt. Feeny and Seamus have apparently set up this trap to rob Barry. It seems to be impossible for them to get there so quick and and even have the time to set up the trap.

When Barry disguises himself as Lt. Fakenham to desert from British army, he should have riding boots. Instead, he wears the gaiters that soldiers serving on foot wore. That would stand out, to any soldiers of the day, and lead to his immediate detection. (Potzdorf, for example, wears riding boots; as a captain, his rank would require him to ride.)

Lord Wendover is introduced to Barry as "Gustavus Aldophus, Earl of Wendover". However, later on when Barry (now in disgrace) attempts to persuade the Earl to join him for lunch in the Club dining room, he addresses him twice as "Neville".