just searched and found this text next to a photos very similar to that bit....
Curb bits
Bits that possess shanks. They utilize leverage to create pressure on the poll and under the chin (via a chin strap), and to also exert more pounds of pressure on the horse's mouth than a snaffle would. Each time you pull back on the reins of a curb bit, the pounds of pressure you use is amplified to the horse. For example, say you exert 1lb of pressure on the rein with your hands, your horse actually feels 10lbs of pressure, courtesy of the shanks.
It's a double bridle.
Bradoon and a curb bit with curved cheeks, sometimes called a Spanish curb.
The curb works the same as a straight cheeked weymouth (draw an imaginary line down the cheek piece)
The curb has a swan neck cheek which used to be popular with show hack exhibitors, bizarrely it is being used with what looks like a nickel flat ring bridoon.