Adios Sabata (movie, 1970)

Set in Mexico under the rule of Emperor Maximilian I, Sabata is hired by the guerrilla leader Señor Ocaño to steal a wagonload of gold from the Austrian army. However, when Sabata and his partners Escudo and Ballantine obtain the wagon, they find it is not full of gold but of sand, and that the gold was taken by Austrian Colonel Skimmel. So Sabata plans to steal back the gold.