the problem is this:
Ptychochromis oligacanthus has many varieties.
some occur on the island of Nosy Be, some on the mainland of Madagascar
however, even the "Nosy Be" is not a single variety, but this island has several small lakes.
and each and every lake has a different variety of the P oligacanthus!
the best known and most often bred is from the lake Bempazava. this one is also known as "Red Fin Nosy Be" or "oligacanthus Red Fin"
in full it would be the jawbreaking "Ptychochromis oligacanthus "Nosy Be Lake Bempazava".
I don't think your fish is from Lake Bempazava, however. those have pinkish fins and a lot of dark on the body. females are often very dark. old males have elongated fins, but most often still a dark vertical band on the sides.
other varieties of Ptychochromis oligacanthus include Lake Ampombilava, also on Nosy Be island, this one has a very typical dark band on the gill cover.
the golden sheen on the side is odd. I've seen a fair number of adult Bempazava and I've never seen any with that amount of gold sheen onm the scales.
"And he piled upon the whale's white hump the sum of all the rage and hate felt by his whole race. If his chest had been a cannon, he would have shot his heart upon it"