Recently I stumbled across this bit, and was rather puzzled by it. It is ported, but has no way of engaging the port. So what does it do?
The standard answer is “tongue relief.” However, a narrow port like this does not actually provide significant tongue relief, no matter what the fans say. The corners where the bar of the mouthpiece meets the port actually create more pressure on the tongue, particularly if only one rein is used.
It is possible, even likely, that this bit is displayed “inside out.” Although the toggles attached to the rings above the nose may have attached to a front portion of the bridle, originally attached to the face plate, configured something like these:
I’ve never seen a bit hung from the nose, and it does seem particularly strange for a loose ring. Of course, you probably noticed that neither of these actually attach to the bit. Even with that stabilizer bar, the bit would fall into the front teeth. It’s possible one or more of the attachments to the ring are fixed, but if not the whole configuration was likely flipped, with the toggles attached to cheek pieces and the bulk of the ring behind the mouthpiece, almost like an oversize baucher, which keeps the bit from pulling through the mouth or into the upper molars: