An old steel ring bit.
This severe mouthpiece with its high port and ring that acts as a curb is also known as a "Mameluke" bit.
This example is handforged in iron or steel which has acquired a rich brown patina.
It has one floral silver boss or dome decorating a cheek, the other is missing, originally there would have been 8 silver studs on each cheek, many are now lost.
I have another example which still has the fine handmade chains which would link behind the curb.
The bit has a high port with wires across which support copper rollers.
There is a curved slobber or shackle bar, one rein loop is damaged

Dimensions of bit : Mouthpiece 10cm (4")
Cheeks 20.5cm (8")
Overall length 24cm (9")
Weight 244g (8½ oz)