As is the case with most big-screen depictions of the famous Gunfight at the OK Corral, there are many historical inaccuracies in this film, not least of which showing Ike Clanton and Morgan Earp dying during the shootout when in fact they both survived the event.
The Katie Elder character name (played by Faye Dunaway) was taken from one of many aliases used by Doc Holliday's actual common-law wife from 1877-1882, Kate Haroney.
Wyatt is shown with the Long Barrelled 'Buntline Special'. There is no historic record of him ever actually possessing it.
When Doc is teaching the Kid to shoot, the Kid fires three rounds by "fanning" his revolver. After a bit more instruction, the Kid fires six more rounds from his 1851 Colt Navy revolver -- without reloading a handgun that holds only six rounds.
In the scene where Doc is teaching the Kid to shoot, the Kid has a holster belt with cartridge ammo in the loops. The Kid's revolver appears to be a Colt 1851 Navy model, which was originally designed with six chambers, each to be loaded with black powder, bullet, and a percussion cap, all separate components rather than in one cartridge. However, by 1881, many of these older Colt revolvers had been converted to cartridge-loaders, so the Kid's cartridge belt is not out of place.
As Earp breaks up a fight in the watering trough he hits one of the cowboys with his right-hand side gun which has a specially long barrel. As he is re-holstering his gun it is bent out of shape.
When playing a card game, Doc bets his horse against Kate. When Doc shuffles the cards, he lays them on the table for Ike to cut. Ike cuts the deck to Doc's left. The camera angle when Doc picks up the cards, is from behind him and Doc picks the cards on the left and puts them back on the deck the way they were before Ike cut them.
After Doc pays and leaves for Tombstone the scene turns to the keeper who mutters something in Spanish. To his right a car can be seen driving through the mountains far in the back.