This looks as if it could be a hybrid between Pearlscale Angelfish (Centropyge vroliki) and Blacktail/Eibl's Angelfish (C. eibli). Such hybrids are known to occur in the wild. This specimen resembles an eibli but with much-reduced striping and without the yellowish 'chest' that the species usually has.
'Redstripe Angelfish' is yet another name for the Eibl's Angelfish/Orangelined Angelfish/Blacktail Angelfish (Centropyge eibli).
In that species, the striping on the body is more pronounced, and the anal fin is lighter in colour, than the specimen shown in this photo. That's why I'm advocating the hybrid vroliki/eibli theory.
In areas like Bali where C. vroliki greatly outnumbers C. eibli, hybrids between the two species are very frequent, as the less common species is forced to breed with the more common one. Also, hybrids between eibli and vroliki are not sterile, and can breed with other hybrids, or back-cross with each of the parent species, producing a whole range of fish with varying degrees of hybrid-traits.
