The reverse designs of these coins do look similar: Rome Denarius Trajan - Parthico Mars Obverse: Laureate bust right, slight drapery on far shoulder IMP CAES NER TRAIANO OPTIM AVG GER DAC Reverse: Mars advancing right with trophy and spear PARTHICO P M TR P COS VI P P SPQR Struck: AD 116-117, Rome mint Catalog: RIC 331, Commemorates the Roman conquest of Parthia (now Iraq) Solomon Islands 5 Cents 2005 - Ngorieru Obverse: Queen Elizabeth II Reverse: Ngorieru, chief of the island sea spirits These sea spirits were sometimes depicted as having human heads and fishlike bodies with gills
That's an interesting contrast. I've barely started researching ancient coinage, but I've been struck with how much modern designs are indebted to Roman paradigms. Going from Mars to Ngorieru might be a bit of a stretch though. Mars was the god of war, and a major player in the pantheon, whereas from what I've read, Ngorieru is merely the ringleader of a gang of mischievous sprites.
