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 dark patina.
The bit has a high port with wires across which would once have supported rollers.
The top of the port has primitive incised decoration in the form of a scallop shell.
A slightly egg-shaped ring hangs from the top of the port. This also has two stripes of incised decoration.
There is a stud on the lower edge of the ring and a hole which would have held another stud.
There is a curved slobber or shackle bar - interestingly this curves upwards, so it is difficult to see how it would fit.

Dimensions of bit : Mouthpiece 10cm (4")
Cheeks 7.6cm (3")
Overall length 25cm (9¾")
Weight 316g (11¼ oz)