It's trace chain, used with horse and mule harness.
This is trace chain, WW1 era with US swivel, note the ring.
And this is trace chain. There are chain "traces," and there are "trace" chains. A chain trace is the entire tug is made up of chain. Trace chains are attached to the end of leather "tugs."
Note the trace chains at the end of the tugs, down near the horses back feet.
BosnMate is probably dead on with the identification! However, I have seen identical chains attached to animal traps and the large ring would either be secured to the ground with a peg or tied to a tree with a rope.