So coming in to briefly sidetrack that Steve Guerdat is actually using what’s called a “Wilson Bit” with his horse from Paris.
There’s a good variety of types on the “Jump In” bit catalog:
https://www.jump-in.fr/fr/content/9-catalogue-mors
Page 35.
His bit appears to be more this variety:
https://www.abbeyengland.com/bits/driving-bits/wilson/
From that website…
" The reins are attached around both rings on each side, as this will limit the amount of inward squeezing action by them. For a stronger action, the reins can be attached to the outside rings only. This would make the bit much more severe, as the inner ring will have the potential to squeeze inward upon the mouth and jaw even more."
Em