What is that extra metal piece in the horse's mouth? It looks to be on it's own strap over the poll.
Looks like a double bridle but doesn't have reins attached.
Its a type of tongue tie bit. It has a bit attached that has a U which sits up along the tongue towards the back of the throat and prevents the horse getting its tongue over the bit.
I agree with phoebetrainer. It likely looks something like this on the inside: http://www.equiport.co.uk/products/d...ngue_grip/892/
Well, I learned something new today! I've never seen that rig before.
Ah-ha! That's it! Thanks--had never seen anything like that before.