Its not dressage legal because it has moving parts (i.e the rings) and the surface of the bit isn't smooth - it has those little lumps on either side of the central bone.
i hve a feeling that it is a copper ringed french link loose ringed snaffle or something along those lines and no it is not dressage legal due to moving parts. the copper is supposed to make horses salivate more and so be easier and more relaxed in the mouth. the loose rings on the bit rings and in the middle allow the horse to paly more with the bit and so hopefully keep it a bit happier in the mouth and the little french link will lie flat on the horses tongue and not have such a severe action as a jointed snaffle due to the lacking middle joitn and so no nutcraker action. some horses like them and some it has no difference with. i think these are also avialable as sweet iron bits which have the same effect.
The rings just make it a nice thing for the horses to play with.
Single jointed snaffles are horrid IMO. The nutcracker of the single joint squeezes the tongue. Try putting a bit across the inside of you elbow and pull on the rings to get some idea of what it feels like for the horse.