Karen, if one googles [bits] especially if they include snaffle, but even "bits" alone, and examine the ones now available one sees that indeed there is some movement in the direction of this bit shape.
Your question about the development and rein handing methods is thought provoking. I suspect that at one time, indeed as ancient art shows, the horse was ridden with more careful rein handling and indeed had as a result a properly conformed neck, with a break at the poll or just behind it.
At the risk of appearing classist I will say that where wealth and power prevail, say as in the Spanish nobility and in our own U.S. West Spanish held territories in the past, where life was, for certain classes, more leisurley time was taken to ride the horse in better form - or I should say in the current vernacular, "frame."
The warrior classes of the collective group called Mongols (many other tribes made up this group) had just such leisure themselves. They did not need to toil, not even hunt if they didn't wish to, but simply took, by either pillage or tribute from conquered peoples.
Thus plenty of time to ride as sport and develop the style and handling more like we are accustomed to.
Those who were poor though having access to horses hadn't the time aside from labors to practice any niceties.
The bit, I'm guessing, hasn't changed much, but just like our own bit styles can be used in at least two extreme ways, haute ecole, or rough and less refined handling so can this one.
I believe that Sue commented that it could be used with the nose lower and the mouthpiece on the bars. In fact I think it's really designed for this, and originaly to help "set," the head.
It has, if I understand the pictures of the horses, a feature that relates to La Jaquima - the bosal fitted hackamore, in that properly fitted and hung, it would, when the horse had a desired headset, offer not pressure on the horse's mouth and tend to hand loosely, as the bosal similarly hangs with no contact around the horses nose when his head is set.
In this case, as in La Jaquima con Fiador, on a loose rein, and with the desired headset it would be a very humane and gentle tool, comparatively.
Just as an improperly fitted and hung bosal this, in rough unsteady hands, results in nose high and forward to escape bar pressure - with the bit, bars of the inside of the mouth, with the bosal, bars under the jaw on the outside, and of course across the nose.
The toklat line and others have moved toward this sort of mouthpiece, but as yet I have not seen any end ring on a curved to the rear extension.
As you know I do not use bits on my own horses but since I teach and many do use bits (unless I can convince them otherwise
) I have to be current on designs and effects.
In fact just advised in a bit purchase for one student's horse. <grumble grumble> but at least she is developing educated hands, is on the road to lightness of aids, and will continue to be under my horse handling influence for yet more time. This is "horse doesn't comply, get a harsher bit," country you see.
I wonder how much damage can be done with this asian bit given how it hangs in the horses' mouth and how it tends to rotate to a neutral position when at rest with no rein pressure?
Donald, Altea, and Bonnie Bitless Cupcake