In this story set in 15th century France, a character wears glasses kept in place with strings that loop around the ears. That type of eyeglasses was invented in Spain during the reign of Philip II in the 16th century.
Esmeralda is tortured in a class of iron vise called the boot, or "brodequins," that is tightened around her foot by screws to crush bones. Actually, Victor Hugo's text notwithstanding, this type of boot did not exist in the 15th century. The boot was conducted by binding a close arrangement of carefully shaped wooden boards around the naked foot and calf of the victim, after which thin, sharp wooden wedges were slowly hammered into the boot, increasing the pressure until the foot bones shattered.
The prologue tells us the story takes place in the 15th century during the reign of King Louis IX. Louis IX reigned from 1226-1270. However, the end credits correctly lists Harry Davenport as having played King Louis XI, who reigned during the period the story takes place, from 1461-1483.