A fanon is the same thing as a royalin. There are also half and double fanon/royalin.
I think the reason for the double name is the bishop of São Tomé. He was apparently responsible for the French settlements in the catholic hierarchy. There is correspondence, in which the bishop protests against any hindu symbols on French colonial coins. This was against French interests, as they just wanted the coins to circulate and didn't care why. Their coins are sometimes somewhat ambiguous on this point. Consider the crown. I presume the bishop was left with the impression that it is the French crown (hence the name royalin, maybe?) However, in modern documents, it is referred to as a "hindu crown". How about that?

Peter