This is a steel bit plated in nickel or chrome.
.
It is a straight bar loose ring snaffle with a central rotating disc.
The disc has a pendant with three holes in it
Metal "keys" or players are suspended from each of these holes.

There is a raised section around the circumference of the mouthpiece, but only on one side.

The bit has round loose rings, which can turn. Each ring has a ridge which would limit rotation when in contact with the cheekpiece

There are no maker's marks or stamps.
Such bits were used when breaking in, the moving parts were supposed to encourage the young horse to relax its mouth. 

Dimensions of bit : Mouthpiece 12.5cm (5"), Total width 11½" (29,5cm), 
Weight 416g (14½ oz)