My understanding of the Chifney bit is that it isn't so much a riding bit as a leading aid. Sort of like a step up when a chain shank doesn't do the job. The two side rings clip or buckle to a halter or headstall, and the lead rope is attached to the third ring, with part of the big "ring" in the horse's mouth. If the horse goes up, it has more bite than a chain over the nose. I think they're a little more common in Britain and Europe than here in the US, and a couple of (very dated) books I've read on halter classes recommend the chifney for fussy show stallions in the ring.
A stubborn horse walks behind you, an impatient one in front of you, but a noble companion walks beside you ~ Unknown