This is a hand forged iron or steel bit with a dark aged patina.
It has a twisted mouthpiece which is curved with a central hinge.
The shape is similar (but not identical) to the "Taylor's simple bit" illustrated in Latchford's "The Loriner".
It has four rings, in the style of a Wilson snaffle.
Dimensions of bit : Mouthpiece 15.5cm (6"), Rings 8cm (3")
Weight 436g (15½ oz)
Ref : bit853