As for rarest, it's different for each person. For me, Platinum Silver wouldn't be rare. Any color mutation of an Aro is rare if there is hardly any in other country. For example, Platinum Jardini, Albino Black, etc.
It's just a Jardini with unique marking, could be a certain bred or WC from a specifc place in Australia. That's the 2nd one of that kind I've seen.