What is a Mullen Mouth?

Question

Due to a foot-and-mouth disease outbreak in Britain at the time of the 1956 Melbourne Olympic Games and the strict quarantine laws of Australia, where were the equestrian events held?

Answer 1

A bit used for riding a horse, and occasionally in dressage
The Mullen Mouth bit is slightly arched to accommodate the horse's tongue but is unjointed; it is seen milder in its effect for the horse and likely to encourage the horse to raise his poll.