This handforged bit made of steel, it probably dates from the 19th Century and has a dark patina..
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It is a straight bar loose ring snaffle with a central "tab".
The tab has two holes in it
Metal "keys" or players are suspended from each of these holes.

The bit has round loose rings, which can turn. Each ring has an S-shaped loop attached - presumably so that the bit could be detached from the headpiece as in a watering bit

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 14cm (5½"), Total width 13½" (34cm), 
Weight 629g (1lb 6 oz)