Goofs

When Mantas shoots the pedals off the flower, the bullets leave no marks on the white adobe wall beyond.

At the 1h 20min mark in the movie, when Sabbath catches up with Angelo on the wagon, you can see overhead lattice power transmission lines in the background. This wouldn't have been possible in the time period depicted in the movie.

Joe Fossit threatens Trixie and Angelo with an Italian stiletto switchblade, a knife style that did not emerge until the early 20th century in Italy.

During the opening stagecoach chase, gunshot sound effects are out of sync with the muzzle flash and smoke from the stuntmen's rifles.

Mantas' goons confront Sartana in Appaloosa and tell him to keep his hands away from the loaf of bread, an apparent reference to the previous scene in which he hid his gun in the bread. The henchmen could not have known about this, as the cantina owner--the only surviving witness--had no apparent opportunity to describe this incident to them.