That's a renaissance-ish 3/4 harness. There were specific tournament battles fought "at the barrier", so they often didn't wear the lower 1/4 or lower 1/2 of armor, since blows were not to be struck below the barrier (fence). I don't know if it's the exact technical term for it, but I generally call that "cavalier armor"; 16th or 17th century, during the age of firearms.