I literally just ran into this after you posted it, over on militaryphotos.net, the person who posted claims it’s from the Congo, not Nigeria. Anyone know for sure?
I know very little about the Nigerian Civil War but what I was able to find on this photo is the names of the photographed. They’re Marc Goosens, Taffy Williams and Armand Ianarelli. Williams served in the Congo under Hoare but Goosens was killed in Nigeria. The camo of Goosens and Ianarelli is also the same stuff used by Biafran troops.