After singing "L'amour est un oiseau rebelle" Carmen picks a rose from a nearby bush and throws it at Don Jose's feet. However, before the song started she had already picked a rose from another bush: during "L'amour est un oiseau rebelle" she can be seen holding it in her right hand until she suddenly doesn't in a different shot.
The story is supposed to take place in the 1820's. The rifles the smugglers use are lever action repeating rifles, first introduced in the 1870's. The pistols they banish appear to be modern percussion cap guns first introduced in Italy in 1833. Colt patented his design in 1835.
Some of the castle and arena scenes seem to have had the top of the structure removed. What remains is a blurry black shadow at the top of the structures.
During the night scene at the gypsy camp where Escamillo makes a stop, you can see car lights on the distant hillside driving on a cliff side road. You can see red tail lights of cars going up as well as a dozen white headlights coming down the road.