I use an eggbutt version of that and it was advertised as a half-moon lozenge-link snaffle (bit of a mouthful!). Not much different to a normal lozenge or even French link to be honest.
Pessoa loose-ring copper moon link snaffle.....learn something everyday lol! Bought it last week and it's working wonders and he loves it. I didn't have a clue when what it was when I bought it, neither did the tack shop lady...it was a one off single one left in a rack of odd bits.